Técnica de alta pressão aplicada à compactação de pós nanométricos

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Síntese de xerogel de sílica sobre matriz de sílica comercial

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Treatment and characterization of biomass of soybean and rice hulls using ionic liquids for the liberation of fermentable sugars

We investigated the changes in the physical structure of cellulose recovered from soybean and rice hulls treated with the ionic liquids 1-butyl-3-methylimidazolium chloride ([bmim][Cl]) and 1-butyl-3-methylimidazolium acetate ([bmim][Ac]). The characterization was carried out by a combination of thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Regenerated cellulose from soybean hull showed loss of crystallinity and high structural disruption caused by both ionic liquid treatments as compared to the untreated material. In contrast, rice hull presented only a small structural disruption when treated with [bmim][Ac] and was practically unaffected by [bmim][Cl], showing that this biomass residue is recalcitrance towards physico-chemical treatments, possibly as a consequence of its high composition content in silica. These results suggest the use of soybean hull as a substrate to be treated with ionic liquids in the preparation of lignocellulosic hydrolysates to be used in second-generation ethanol production, whereas other methods should be considered to treat rice hull biomass

Preparação de gel de sílica sobre sílica comercial

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Compactos de sílica dopados com rodamina 6G

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Estudo morfológico do xerogel híbrido dabco/sílica

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High performance biocatalyst based on β-D-galactosidase immobilized on mesoporous silica/titania/chitosan material

A new support for the immobilization of β-D-galactosidase from Kluyveromyces lactis was developed, consisting of mesoporous silica/titania with a chitosan coating. This support presents a high available surface area and adequate pore size for optimizing the immobilization efficiency of the enzyme and, furthermore, maintaining its activity. The obtained supported biocatalyst was applied in enzyme hydrolytic activity tests with o-NPG, showing high activity 1223 Ug 1, excellent efficiency (74%), and activity recovery (54%). Tests of lactose hydrolysis in a continuous flow reactor showed that during 14 days operation, the biocatalyst maintained full enzymatic activity. In a batch system, after 15 cycles, it retained approximately 90% of its initial catalytic activity and attained full conversion of the lactose 100% (±12%). Additionally, with the use of the mesoporous silica/titania support, the biocatalyst presented no deformation and fragmentation, in both systems, demonstrating high operational stability and appropriate properties for applications in food manufacturing

Tuning anatase-rutile phase transition temperature : TiO2/SiO2 nanoparticles applied in dye-sensitized solar cells

TiO2/SiO2 nanoparticles with 3, 5, and 10 molar percent of silica, were synthesized by hydrothermal method and characterized by SEM, TEM, N2 adsorption-desorption isotherms, X-ray diffraction, and Raman and UV-Vis spectroscopy. While pristine TiO2 thermally treated at 500°C presents a surface area of 36 m2g-1(±10 m2g-1), TiO2/SiO2 containing 3, 5, and 10 molar percent of silica present surface areas of 93, 124, and 150 m2g-1(±10 m2g-1), respectively. SiO2is found to form very small amorphous domains well dispersed in the TiO2 matrix. X-ray diffraction and Raman spectroscopy data show that anatase-to-rutile phase transition temperature is delayed by the presence of SiO2, enabling single-anatase phase photoanodes for DSSCs. According to the I×V measurements, photoanodes with 3% of SiO2 result in improved efficiency, which is mainly related to increasedsurface area and dye loading. In addition, the results suggest a gain in photocurrent related to the passivation of defects by SiO

Síntese e caracterização do xerogel híbrido fenilenediaminapropilsílica

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Síntese e caracterização de um novo material híbrido a base de sílica e celulose

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