D.H. Aguilar

Photothermal characterization of materials biomineralized by mollusks (invited)

In this article the potential of photoacoustic techniques in the optical and thermal characterization of mollusk-made biominerals is explored. The case of two bivalve species with strong structural and architectural differences, oysters (Crassostrea virginica) and mussels (Ischadium recurvum) is considered. The difference between them is closely related to the dominance of different polymorphs of calcium carbonate in crystalline phases known as aragonite and calcite. The thermal diffusivity, visible and infrared absorption spectra, and x-ray analysis show differences between aragonite and calcite made biominerals. Photoacoustic spectra show absorption bands related to Fe, Mn, and organic pigments.

Phase Structure and Thermal Evolution in Mixed Oxide TiO2-ZrO2 Powders Obtained by the Sol-Gel Process

In this work we present the phase structure evolution, with long annealing times, of mixed oxides powders in the TiO2-ZrO2 system, obtained by the sol-gel method. Several compositions were synthesized via the catalytic hydrolysis of titanium and zirconium butoxides, HNO3 was added to adjust the pH=3. Pure zirconia and titania were also prepared. Long thermal treatments were applied from 100–1000°C, increasing the temperature every 100°C. These samples were heated during 20 h at each temperature.

Thermal Stability and Hydrolysis Catalysts Effect on Sol-Gel Zirconia in The Presence of Heteropolyacids

Zirconia catalysts with 15 and 25 wt% of tungstophosphoric acid (TPA) were prepared by the sol gel method. The gels were obtained by catalytic hydrolysis of zirconium n-butoxide and TPA, at pH= 3, 5 and 7, using as catalysts HCl, C2H4O2 and NH4OH, respectively. Fresh samples were thermally treated from 100°C to 900 °C, in a stepwise increments of 100°C, during 20 hours per step. The crystallization behavior was followed by powder X-ray diffraction.

E.coli Geneticaly Modified and Encapsulated in Sol-Gel Silica

In the present work is encapsulated in sol-gel silica, Exoli which has been genetically modified. This bacterium without modification has been extensively studied into sol-gel silica. Nevertheless, this work shows the results of the synthesis parameters research to maintain the modified microorganism alive.