Showing papers by "Eduardo Radovanovic published in 2008"

Organic–inorganic hybrid materials derived from epoxy resin and polysiloxanes: Synthesis and characterization

Abstract: In this study, hybrid materials based on epoxy resin were prepared as transparent self-supported films by a sol–gel process. 4,4′-Diaminodiphenylmethane or oligomeric epoxy resin were used as precursors, which were conveniently functionalized with trialkoxysilanes as end-groups. The effect of the introduction of poly (dimethylsiloxane) was also investigated. The hybrid films showed good thermal stability, a nondefined glass transition temperature, and a dense morphology without phase segregation. The tendency to a flat surface could be observed by atomic force microscopy. The hybrid films also showed good performance as coatings for glass plates, with an improved hydrophobic character in comparison to neat epoxy resin. POLYM. ENG. SCI., 48:141–148, 2008. © 2007 Society of Plastics Engineers

Chemical characterization of BiFeO3 obtained by Pechini method

Abstract: This work describes the synthesis and characterization of BiFeO3 obtained by the Pechini route using bismuth nitrate and iron nitrate as precursors. The powders were annealed at 800 °C in air for 2 h. X-ray diffraction patterns showed that the material presents two phases, BiFeO3 (95%) and α-Bi2O3 (5%). The ferroelectric transition of the sample at 821 °C was detected by differential thermal analysis. Results of analyses by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and energy dispersive X-ray fluorescence (EDX) showed that the sample is chemically homogeneous. Transmission electron microscopy images revealed that the sample is uniform and contains spherical particles with an average size of 30 nm.

Synthesis of Ag-PVA and Ag-PVA/PET-s20 composites by supercritical CO2 method and study of silver nanoparticle growth

Abstract: Supercritical CO2 has been used to prepare silver polymer composites, silver/poly(vinyl alcohol) and silver/poly(vinyl alcohol)/sulfonated poly(ethylene terephthalate) through impregnation of a silver precursor in solid-state polymeric matrices followed by thermal reduction of the silver precursor. X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, thermogravimetric analysis and UV/vis spectroscopy indicate that synthesis conditions and polymeric matrix composition affect silver particle size, shape and distribution in polymeric matrices. Silver particles are smaller, have a more uniform shape and present narrower size distribution in PVA-rich than in PETs-rich composites.

PAAm and PEDOT/PSS hydrogel as potential electroactive devices: evaluation of surface and hydrophilic properties

Abstract: Abstract The aim of this work was to analyze the hydrophilic and surface properties of semi-IPN hydrogels with good electroactive properties based on poly (acrylamide) (PAAm) and conductive polymer poly(3,4-ethylene dioxythiophene)/ poly(styrenesulfonate) (PEDOT/PSS). The hydrogels properties were analyzed by degree of swelling (DS), drop water contact angle (DWCA) and atomic force microscopy (AFM). In addition, the state of water in the hydrogels was estimated by differential scanning calorimetry (DSC) analysis. Results revealed that the presence of PEDOT/PSS reduce the hydrophilicity of the network, mainly those prepared with lower cross-linking density, demonstrating that PEDOT/PSS chains (or their segments) are displayed in surface hydrogels. The possibility of producing PAAm-PEDOT/PSS hydrogels with controlled properties in a desired range of values is of key importance to optimize its use in several applications, mainly in optical devices, capacitors, artificial muscles, and rechargeable lithium batteries