Estudo do processo SOL-GEL para a obtenção de xerogéis e aerogéis monolíticos

O presente trabalho descreve uma pequena parte da história do Processo Sol-Gel e sua implantação em nosso Departamento. É dedicado ao estudo do processo para a preparação de Xerogéis e Aerogéis monolíticos de Sílica, puros e dopados. O processo compreende a hidrólise ácida do Tetraethoxisilano estimulada por ultra-som e subseqüente policondensação, envelhecimento e secagem em condições normais (Xerogéis) e via extração hipercrítica do CO2, (Aerogéis). Também descreve de maneira sucinta, a química do processo Sol-Gel dos alcooxisilanos e os possíveis produtos, sua nomenclatura, algumas vantagens e desvantagens. Apresenta um método original que permite identificar os parâmetros que influenciam as reações de hidrólise dos alcooxisilanos e determinar as melhores condições experimentais para a obtenção de amostras monolíticas. Descreve também a técnica de preparação de aerogéis via extração hipercrítica do CO2 e caracterizações óticas e térmicas de várias amostras obtidas em nosso laboratório. O processo Sol-Gel, não é um método adequado para a produção de grandes quantidades de produtos de uso comum. Também não substitui os processos industriais convencionais, mas torna-se particularmente interessante para a preparação de materiais vítreos impossíveis de serem preparados por técnicas convencionais de fusão, como é o caso das matrizes de SiO2 dopadas com polímeros e corantes orgânicos.

New insights for materials science characterisation using different complementary techniques combined with x-ray absorption spectroscopy

The combination of x-ray absorption spectroscopy (XAS) with UV-Vis and Raman spectroscopies or with Differential Scanning Calorimetry (DSC) has been recently carried out on the D44 beamline of DCI-LURE. The different set-ups used to perform such combinations are described and examples of combined investigations belonging to different field of materials science (coordination chemistry, sol-gel and catalysis) are presented. © Physica Scripta 2005.

Estudo das propriedades ópticas e estruturais de espinélios do tipo 'ZNAL IND. 2 O IND. 4' contendo 'EU POT. 3+' ou 'TB POT. 3+'

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese de cerâmicas nanoestruturadas híbridas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo do potencial de associações de ZnO com os produtos naturais ácido cafeico e ferúlico como filtros solares híbridos: [recurso eletrônico]

In this work were studied associations of ZnO with the natural products caffeic and feluric acids. Two preparation methods were used, that is, the sol-gel and a reflux procedure. In the sol-gel method, ZnO is produced by the basics hydrolysis of precursors in the presence of the organic filters (caffeic and feluric acids), which results in 30 nm (or less) ZnO particles with the organic filters (in dissociated form) bonded to the surface of ZnO. In the reflux method, a dispersion of ZnO in a water/ethanol mixture was kept under reflux (50oC/4h) in the presence of the organic acids. The ZnO particles used in the reflux method have a higher diameter than sol-gel ZnO particles, but the prepared associated product ZnO/Organic acids were similar. Despite of the difference in relation to crystallinity between the products, the preparation methods resulted in analogous associations with respect to the interaction of the organic filters with the ZnO surface. The caffeic/ZnO associations presented low photostability, which lead to the degradation of the organic filter. The other associations (feluric acid/ZnO) presented satisfactory results. The FT-IR spectroscopy confirmed the formation of the association, and the nature of the bond formed compared with the Zn-O bond in Zn2+/Felutic acid complexes. The isolated organic and inorganic filters, along with the associations were analyzed by diffuse reflectance spectroscopy and Uv-vis spectroscopy. The absorption edges and the critical wavelengths were analyzed and the effects of Zn-O bonds in feluric acid/ZnO associations described as a function of the relative position of the π/π* system of the organic filter. Finally the performance of the hybrid filters were investigated in terms of the absorption of UVA and UVB radiations, with the UVA/UVB ratio, an efficiency parameter largely used in the description of solar filters, sunscreen and suncare products

Design of hierarchical porous aluminas by using one-pot synthesis and different calcination temperatures

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Controlling the growth of zirconia needles precursor from a liquid crystal template

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Preparação de espuma cerâmica à base de zircônia pelo processo sol-emulsão-gel

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Preparação de espumas cerâmicas de 'TIO IND. 2' a partir do processo sol-emulsão-gel

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Structure and catalytic properties of sulfated zirconia foams

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Correlation between structural and catalytic properties of copper supported on porous alumina for the ethanol dehydrogenation reaction

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Rheological, mechanical and mucoadhesive properties of thermoresponsive, bioadhesive binary mixtures composed of poloxamer 407 and carbopol 974P designed as platforms for implantable drug delivery systems for use in the oral cavity

This study described the formulation and characterisation of the viscoelastic, mechanical and mucoadhesive properties of thermoresponsive, binary polymeric systems composed of poloxamer (P407) and poly(acrylic acid, C974P) that were designed for use as a drug delivery platform within the oral cavity. Monopolymeric and binary polymeric formulations were prepared containing 10, 15 and 20% (w/w) poloxamer (407) and 0.10-0.25% (w/w) poly(acrylic acid, 934P). The flow theological and viscoelastic properties of the formulations were determined using controlled stress and oscillatory rheometry, respectively, the latter as a function of temperature. The mechanical and mucoadhesive properties (namely the force required to break the bond between the formulation and a pre-hydrated mucin disc) were determined using compression and tensile analysis, respectively. Binary systems composed of 10% (w/w) P407 and C934P were elastoviscous, were easily deformed under stress and did not exhibit mucoadhesion. Formulations containing 15 or 20% (w/w) Pluronic P407 and C934P exhibited a sol-gel temperature T(sol/gel), were viscoelastic and offered high elasticity and resistance to deformation at 37 degrees C. Conversely these formulations were elastoviscous and easily deformed at temperatures below the sol-gel transition temperature. The sol-gel transition temperatures of systems containing 15% (w/w) P407 were unaffected by the presence of C934P; however, increasing the concentration of C934P decreased the T(sol/gel) in formulations containing 20%(w/w) P407. Rheological synergy between P407 and C934P at 37 degrees C was observed and was accredited to secondary interactions between these polymers, in addition to hydrophobic interactions between P407 micelles. Importantly, formulations composed of 20% (w/w) P407 and C934P exhibited pronounced mucoadhesive properties. The ease of administration (below the T(sol/gel)) in conjunction with the viscoelastic (notably high elasticity) and mucoadhesive properties (at body temperature) render the formulations composed of 20% (w/w) P407 and C934P as potentially useful platforms for mucoadhesive, controlled topical drug delivery within the oral cavity. (c) 2009 Published by Elsevier B.V.

Characterization of metallic electrical contacts to SnO2 thin films lightly doped with Eu3+ ions, and photo-induced resistivity

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Investigation in SrTiO3-CaTiO3-PbTiO3 ternary thin films by dielectric proprieties and Raman spectroscopy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Growth of Al2O3 thin film by oxidation of resistively evaporated Al on top of SnO2, and electrical properties of the heterojunction SnO2/Al2O3

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)