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Oligomers of hard and soft segments of unsaturated polyesters (UP) were synthesized. They were blended in different ratios and cured with various amounts of styrene. Based on the criteria of tensile strength and strain, hard segment/soft segment (60/40 wt %) UPs containing 35 wt % and 45 wt % of extra amount of styrene were chosen for further studies. Inorganic-organic hybrid materials were prepared by incorporating tetraethoxysilane and poly(dimethylsiloxane) into the UP resins via the sol-gel process by changing the ratios of HCl/TEOS, H2O/TEOS, TEOS/PDMS and the reaction time. The specimens of these hybrid materials after curing were characterized using the tensile tester, rheometer, scanning electron microscope (SEM), 29Si-NMR and thermogravimeter. In the condition of HCl/TEOS molar ratio 0.07, H2O/TEOS molar ratio 4, TEOS/PDMS weight ratio 90/10 and the reaction time 3 hours, the results of 29Si-NMR, SEM and silicone mapping indicate that these silica gels with 3D network were well dispersed in the UP resins. These specimens had tensile strength of 512¡Ó16 kgf/cm2 and elongation of 11¡Ó4 % which are above the criteria of inhibitors. From the erosion testing, flame retardants was added unsaturated polyester and inorganic-organic hybrid materials that can help to resist heat flame, remain of a fire on the surface had the char forming.

Made available in DSpace on 2014-06-11T19:29:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2001Bitstream added on 2014-06-13T19:58:41Z : No. of bitstreams: 1 santos_ep_me_araiq.pdf: 2607932 bytes, checksum: 5c06a620c980880e28b369b2f69e4022 (MD5) / Nesta dissertação analisou-se as condições de formação de espumas cerâmicas a partir de suspensões coloidais à base de zircônia, preparadas pelo processo sol-gel termoestimulado.A formação e estabilidade da espuma foi analisada em função da concentração da suspensão coloidal, concentração de tensoativo, quantidade de agente espumante (Freon11), tempo de maturação e da temperatura de tratamento térmico.A concentração micelar crítica de tensoativo foi determinada por medidas de condutividade e a estabilidade da espuma úmida durante a secagem foi determinada a patir de medidas de retração linear e perda de massa do gel.Diferentes condições de geração de espuma foram testados, onde avaliou-se o volume de espuma formado e sua estrutura.Os resultados evidenciaram que a concentração de tensoativo e de partículas na suspensão são determinantes na formação de espumas cerâmicas a base de óxido de zircônio preparadas a partir do processo sol-gel.Mantendo-se a concentração fixa de tensoativo e de Freon11, variou-se o tempo de envelhecimento da espuma entre 6-240h.A amostra maturada por 192h apresentou densidade real igual a 3,13 g/cm3, aparente igual 0,79 g/cm3 e % em volume de poros igual a 74,8%. Foram geradas espumas com diferentes tipos e concentrações de tensoativo, onde verificou-se uma diminuição da densidade real e aparente, com o aumento da concentração de tensoativo.Análises de espectrometria no infravermelho indicam apenas interações físicas entre as partículas coloidais e as moléculas do tensoativo.Análises por porosimetria de mercúrio permitiram determinar o diâmetro médio dos poros das amostras obtidas e seus valores são próximos aos encontrados na literatura, para espumas cerâmicas.As espumas preparadas com o tensoativo IGEPAL710 apresentam uma distribuição bimodal de tamanho de poros, o que foi atribuído à formação de microemulsão entreo Freon11 eo dispersante aquoso. / In this work the conditions of formation of ceramic foams from zirconia based colloidal suspensions by using the thermostimulated sol-gel process have been analyzed. The formation and stability of foam were analyzed as function of concentration of colloidal suspension and surfactant, quantity of foaming (Freon11), aging time and temperature of thermal treatment. The critical micellar concentration of surfactant has been determined by conductivity measurements and the stability of foam during drying by measuring the linear shrinkage and mass loss. Different conditions of foam generation have been tested, and the volume of foam and its structure have been evaluated. The results evidence that both concentrations of surfactant and of particles in suspension play a key role in the formation of ceramic foams based on zirconium oxide by sol-gel process. For concentration of surfactant and Freon11 fix, aging time has been screened from 6 to 240h. The samples aged for 192h presented real density of 3,13g/cm3 and bulk density of 0,79g/cm3 and 74,8% volumetric porosity. For foams prepared with different kind and concentration of surfactant, it was verified that both real and bulk densities decrease as the surfactant concentration increases. An infra-red analysis indicates only physical interactions between colloidal particles and surfactant molecules. The Hg porosimetry allowed to determine the mean pore diameter of samples, with values are comparable to that reported in literature for ceramic foams. The foam prepared with IGEPAL710 present bimodal pore size distribution what has been attributed to the formation of microemulsion between Freon11 and the aqueous dispersant.

Quantum dots (QDs) of II-VI semiconductors (CdS, CdSe, and CdTe) in the size range of 1~12 nm have attracted great interest in both fundamental research and technical applications in recent years. Due to their tunable size-dependent emission with high photoluminescence quantum yields, their broad excitation spectra and narrow emission bandwidths, the semiconductor QDs have been intensively investigated in versatile applications, including thin-film light emitting devices (LEDs), low-threshold lasers, optical amplifier media for telecommunication networks and biological labels. Thus, constructing and fabricating highly ordered QDs are of great importance in the field of nanotechnology. The surface chemistry behavior of the TOPO-CdSe QDs and TOPO-(CdSe)ZnS QDs at the air-water interface was carefully examined by various physical measurements. The surface pressure-area isotherms of the Langmuir monolayers of both types of QDs gave the average diameter which matched the value determined by TEM measurements. Topographic study of the Langmuir monolayers of both QDs revealed the 2D aggregation during the early stage of the compression process. The stability of the Langmuir monolayer of the TOPO-(CdSe)ZnS QDs was measured by the compression/decompression cycle and the kinetic measurements, both of which indicated that TOPO capped (CdSe)ZnS QDs can form stable Langmuir monolayers at the air-water interface. Langmuir-Blodgett (LB) film of the TOPO-(CdSe)ZnS QDs were prepared on quartz slides at different surface pressures and characterized by photoluminescence (PL) spectroscopy. The linear increase of the PL intensity with the increase of the number of layers deposited onto the quartz slide implied a homogeneous deposition of the Langmuir monolayer. The conjugates of 10, 12-pentacosadiynoic acid (PDA) and short chain peptide was used to modify the surface of (CdSe)ZnS core-shell QDs. The PDA-peptide capped QDs formed stable Langmuir monolayer. After the photopolymerization of PDA-peptide-QDs/PDA-peptide system at the air-water interface, a more uniform and robust Langmuir monolayer was constructed. The 3-mercaptopropyltrimethoxysilane (MPS) was linked to (CdSe)ZnS QDs by ligand exchange method. The sol-gel process of the MPS capped QDs Langmuir monolayer was studied under various subphases of pH and reaction time. The fast sol-gel process under a subphase of pH 12.0 led the formation of a more homogeneous Langmuir monolayer. A smooth MPS-QDs LB film deposited under pH 12.0 was also observed by AFM measurements. The imaging of the aggregates of lysozyme using lysozyme/(CdSe)ZnS QDs conjugate as a PL label was investigated. The amyloid fibrils formed by lysozyme/lysozyme-QDs conjugate were observed by epifluorescence microscopy, atomic force microscopy (AFM) and transmission electron microscopy (TEM) measurements. The emission intensity of the QDs labeled lysozyme was increased about 3 fold after formation of amyloid. This approach, for the first time, provided a convenience method to image the amyloid fibrils by epifluorescence microscopy.

A series of photopolymerizable silica for optical storage has been prepared using sol-gel process in this study. The inorganic-organic hybrid materials were based on methacroloxy-propyl-trimethoxysilane (MPTS) and tetraethylorthosilicate (TEOS). Thin films of the hybrids were prepared using spin coating, knife coating, and the closed-mold methods, while the knife coating showing better film flatness and controlled film thickness. Results indicate crack-free polymerizable silica can be obtained using a recipe with 1 wt% photoinitiator. Samples after irradiation shows increased transmittance, suggesting that photopolymerization did take place with the aid of photoinitiators. Spectroscopic study from FTIR indicates C=C conversion in the acrylic part of MPTS reaches 57.51%. The grating period is observed by the optical microscopy. The maximum diffraction efficiency is 48.21%, as obtained from the sample of pure MPTS. From BET measurements, the pore size of the polymerizable silica increases with the increasing amount of MPTS, consistent with the results from measurements of apparent density. Factors affecting the diffraction efficiency are analyzed; these include sample flatness, sample thickness, the conversion of monomer, and concentration of the photoinitiator. Formation mechanism of the periodic grating is proposed based on this study. Addition of MPTS can greatly alleviate problem of phase separation; yet, movement acrylic segment in MPTS is severely limited. On the other hand, samples with more TEOS tend to be densified more with decreased diffraction efficiency

In this research, manganese oxide based nanoparticles were synthesized by sol-gel process. Methanol, ethanol, and propanol were used as alternative solvents during sol-gel process with manganese acetate as precursor for the preparation of pristine manganese oxide. Hybrid manganese oxide modified by additions of carbon nanotubes was further prepared. The effects of different solutions and heat treatment temperatures on the morphology, physical characteristics, and electrochemical properties of the manganese oxide based materials were investigated. Particle size of pristine manganese oxide samples prepared from methanol, ethanol, and propanol were compared by SEM and TEM image analysis. Smallest particle size was observed for manganese oxide prepared from propanol, with diameters range from 16 nm to 50nm. XRD results showed that the as-prepared manganese oxide based samples treated at calcination temperature of 300ºC and above were composed of Mn2O3 as dominant phase, with Mn3O4 as minor phase. Specific capacitance of manganese oxide prepared from methanol, ethanol, and propanol at scan rate of 10 mV/s measured using two electrode systems were 88.3, 66.0, and 104.8 F/g, respectively and that for the hybrid sample was 140.5 F/g. Results from electrochemical impedance spectroscopy (EIS) also showed superior electrochemical properties of the hybrid sample over pristine manganese oxide samples. It is evident that the addition of carbon nanotubes not only improved the specific capacitance but also the overall electrochemical properties of the manganese oxide supercapacitor.

Made available in DSpace on 2014-06-11T19:25:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-06-08Bitstream added on 2014-06-13T19:32:52Z : No. of bitstreams: 1 reis_fve_me_araiq.pdf: 3936353 bytes, checksum: f0ae31c006486b496b3c681a599a9d65 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho foram estudados métodos para síntese de nanoesferas de sílica com diâmetros entre 10 e 50 nm e com estreita distribuição de tamanho. A síntese das nanoesferas teve como base metodologias existentes na literatura que utilizam aminoácido como catalisador, com o objetivo de se obter um maior controle do diâmetro final e da distribuição de tamanho. A caracterização das amostras foi realizada utilizando-se as técnicas de IV, RMN, BET, Potencial Zeta ( ), QELS, SAXS e FEG-SEM. O estudo da cinética da síntese das nanoesferas revelou que é possível controlar o tamanho e a dispersão das partículas a partir da variação de parâmetros tais como o tempo de reação e a concentração de catalisador utilizado. As medidas de QELS e SAXS “ex situ” mostraram que foi possível obter suspensões coloidais monodispersas de nanoesferas de sílica com diâmetros de partículas entre 10 e 50 nm. As medidas “in situ” mostraram que as nanoesferas crescem de forma homogênea após o processo de nucleação e que o diâmetro final das mesmas depende do tipo e da concentração do catalisador utilizado. Os espectros de IV e RMN mostraram a presença de grupos silanóis na superfície das esferas e as medidas de Potencial Zeta ( ) revelaram a estabilidade do sistema em decorrência da presença desses grupos. As nanoesferas de sílica foram ordenadas na forma de filmes, em monocamadas a partir dos métodos: deposição gravitacional e “dip-coating” em substratos (silício ou mica) previamente dimensionados, limpos e ativados. A partir dos gráficos obtidos por SAXS verificou-se que o diâmetro das nanoesferas, a concentração de partículas em suspensão e a velocidade de emersão influenciam na qualidade dos filmes. Pelas imagens de FEG-SEM verificou-se a formação de arranjos bidimensionais (monocamadas) e tridimensionais... / In this work methods for the synthesis of silica nanospheres showing diameters in between 10 and 50 nm and a narrow size distribution were studied. These nanospheres syntheses were based on methodologies existing in the literature that use amino acid as catalyst in order to better control both the final diameter and distribution. Samples characterization was performed using IR, NMR, BET, Zeta Potential, QELS, SAXS and FEG-SEM measurements. The kinetics of synthesis of nanospheres revealed that it is possible to control the size and the size dispersion of particles by variating parameters such as the synthesis time and the catalyst concentration. The SAXS and QELS ex situ measurements have shown the possibility to obtain colloidal suspensions of monodisperse silica nanospheres with particles diameters in between 10 and 50 nm. Otherwise, the in situ measurements have shown that nanospheres grow homogeneously after nucleation process and that the overall diameter depends on the type and concentration of the catalyst. The IR and NMR spectra analyses have shown the presence of hydroxyl groups on the spheres surface, while Zeta potential ( ) measurements revealed the stability of the system is due to the presence of these groups. The silica nanospheres were ordered in form of films, monolayers, using the methods: gravitational deposition and dipcoating on substrates (silicon or mica) previously scaled, cleaned and activated. The SAXS results have shown that both the diameter and concentration of the particles in suspension and the deposition rate influence the films quality. FEGSEM images have shown both the formation of two (monolayers) and three (multiple layers) dimensional arrays as well as high monodispersity of spheres. The set of information obtained from these systems characterization... (Complete abstract click electronic access below)

Resumo: Nesta dissertação analisou-se as condições de formação de espumas cerâmicas a partir de suspensões coloidais à base de zircônia, preparadas pelo processo sol-gel termoestimulado.A formação e estabilidade da espuma foi analisada em função da concentração da suspensão coloidal, concentração de tensoativo, quantidade de agente espumante (Freon11), tempo de maturação e da temperatura de tratamento térmico.A concentração micelar crítica de tensoativo foi determinada por medidas de condutividade e a estabilidade da espuma úmida durante a secagem foi determinada a patir de medidas de retração linear e perda de massa do gel.Diferentes condições de geração de espuma foram testados, onde avaliou-se o volume de espuma formado e sua estrutura.Os resultados evidenciaram que a concentração de tensoativo e de partículas na suspensão são determinantes na formação de espumas cerâmicas a base de óxido de zircônio preparadas a partir do processo sol-gel.Mantendo-se a concentração fixa de tensoativo e de Freon11, variou-se o tempo de envelhecimento da espuma entre 6-240h.A amostra maturada por 192h apresentou densidade real igual a 3,13 g/cm3, aparente igual 0,79 g/cm3 e % em volume de poros igual a 74,8%. Foram geradas espumas com diferentes tipos e concentrações de tensoativo, onde verificou-se uma diminuição da densidade real e aparente, com o aumento da concentração de tensoativo.Análises de espectrometria no infravermelho indicam apenas interações físicas entre as partículas coloidais e as moléculas do tensoativo.Análises por porosimetria de mercúrio permitiram determinar o diâmetro médio dos poros das amostras obtidas e seus valores são próximos aos encontrados na literatura, para espumas cerâmicas.As espumas preparadas com o tensoativo IGEPAL710 apresentam uma distribuição bimodal de tamanho de poros, o que foi atribuído à formação de microemulsão entreo Freon11 eo dispersante aquoso. / Abstract: In this work the conditions of formation of ceramic foams from zirconia based colloidal suspensions by using the thermostimulated sol-gel process have been analyzed. The formation and stability of foam were analyzed as function of concentration of colloidal suspension and surfactant, quantity of foaming (Freon11), aging time and temperature of thermal treatment. The critical micellar concentration of surfactant has been determined by conductivity measurements and the stability of foam during drying by measuring the linear shrinkage and mass loss. Different conditions of foam generation have been tested, and the volume of foam and its structure have been evaluated. The results evidence that both concentrations of surfactant and of particles in suspension play a key role in the formation of ceramic foams based on zirconium oxide by sol-gel process. For concentration of surfactant and Freon11 fix, aging time has been screened from 6 to 240h. The samples aged for 192h presented real density of 3,13g/cm3 and bulk density of 0,79g/cm3 and 74,8% volumetric porosity. For foams prepared with different kind and concentration of surfactant, it was verified that both real and bulk densities decrease as the surfactant concentration increases. An infra-red analysis indicates only physical interactions between colloidal particles and surfactant molecules. The Hg porosimetry allowed to determine the mean pore diameter of samples, with values are comparable to that reported in literature for ceramic foams. The foam prepared with IGEPAL710 present bimodal pore size distribution what has been attributed to the formation of microemulsion between Freon11 and the aqueous dispersant. / Orientador: Celso Valentim Santilli / Coorientador: Sandra Helena Pulcinelli / Banca: Marian Rosaly Davolos / Banca: João Barros Valim / Mestre

When the inorganic domain sizes in a composite are reduced to a level such that a "molecular composite" is formed, the hybrid materials are commonly referred to as "ceramers". Hybrid materials span from inorganically modified organic polymers to inorganic g1asses slightly modified by organic polymers. The incorporation of an inorganic phase into an organic polymer is done almost exclusively by the "sol-gel" process.

Stable suspensions of superparamagnetic cobalt nanoparticles have been prepared in poly(dimethysiloxane) (PDMS) carrier fluids in the presence of poly[dimethylsiloxane-b-(3-cyanopropyl)methylsiloxane-b-dimethylsiloxane] (PDMS-PCPMS-PDMS) triblock copolymers as steric stabilizers. A series of the polysiloxane triblock copolymers with systematically varied molecular weights were prepared via anionic polymerization using LiOH as an initiator. These copolymers formed micelles in toluene or poly(dimethylsiloxane) (PDMS) carrier fluids and served as "nanoreactors" for thermal decomposition of the CO₂(CO)8 precursor. The nitrile groups on the PCPMS central blocks are thought to coordinate onto the particle surface, while the PDMS endblocks protrude into the reaction medium to provide steric stability. The particle size can be controlled by adjusting the cobalt to copolymer ratio. Ordered self-assemblies of these cobalt nanoparticles are observed when the dispersions are cast from toluene. Electron diffraction spectroscopy reveals that the cobalt nanoparticles have fcc crystal structures. TEM shows non-aggregated cobalt nanoparticles with narrow size distributions, which are evenly surrounded with copolymer sheaths. However, some degree of surface oxidation was observed over time, resulting in a decrease in magnetic susceptibility. Novel poly[dimethylsiloxane-b-methyltriethoxysilylsiloxane-b-(3-cyanopropyl) methylsiloxane-b-methyltriethoxysilylsiloxane-b-dimethylsiloxane] (PDMS-PMTEOS-PCPMS-PMTEOS-PDMS) pentablock terpolymers were prepared. These terpolymers could fill the dual role both as steric stabilizers for preparing stable cobalt nanoparticle dispersions and precursors for the particle coating process. Silica films coated on the particles surfaces were employed to prevent the surface oxidation of the nanoparticles. Specific saturation magnetic measurement indicates that coating the nanoparticles with silica thin films can effectively inhibit the oxidation process. / Ph. D.