NOVEL CELLULOSE/NbOPO4 center dot nH(2)O HYBRID MATERIAL FROM SUGARCANE BAGASSE

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

Preparation and characterization of cellulose/hydrous niobium oxide hybrid

A composite of cellulose extracted from bagasse with Nb2O5 center dot nH(2)O in three different proportions (16.67, 37.5 and 50.0 wt%) was prepared using the co-precipitation method. The materials were characterized by X-ray diffractometry (XRD), Fourier transform infra-red spectroscopy (FTIR), thermogravimetric analysis (TG/DTG), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). TG data obtained show that the presence of inorganic material influenced slightly the stability of the hybrid material. The precipitation of 16.67 wt.% of oxide was sufficient to inhibit the combustion peaks present in the DSC curve of cellulose. This work will help find new applications for these materials. Published by Elsevier Ltd.

Structure and microstructure of PbTiO3 thin films obtained from hybrid chemical method

PbTiO3 thin films were deposited on Si(100) via hybrid chemical method and crystallized between 400 and 700 degreesC to study the effect of the crystallization kinetics on structure and microstructure of these materials. X-ray diffraction (XRD) technique was used to study the structure of the crystallized films. In the temperature range investigated, the lattice strain (c/a) presented a maximum value (c/a = 1.056) for film crystallized at 600 degreesC for I h. Atomic force microscopy (AFM) was used in investigation of the microstructure of the films. The rms roughness of the films linearly increases with temperature and ranged from 1.25 to 9.04 nm while the grain sizes ranged from 130.6 to 213.6 nm. Greater grain size was observed for film crystallized at 600 degreesC for 1 h. (C) 2002 Elsevier B.V. S.A. All rights reserved.

Charge injection in an LED with a hybrid composite as the emissive layer

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

Multi-spectroscopic monitoring of cisplatin-derived species delivery from ureasil polyether hybrid matrix

Driven by the challenges involved in the development of new advanced materials with unusual drug delivery profiles capable of improving the therapeutic and toxicological properties of existing cancer chemotherapy, the one-pot sol-gel synthesis of flexible, transparent and insoluble urea-cross-linked polyether-siloxane hybrids has been recently developed. In this one-pot synthesis, the strong interaction between the antitumor cisplatin (CisPt) molecules and the ureasil-poly(propylene oxide) (PPO) hybrid matrix gives rise to the incorporation and release of an unknown CisPt-derived species, hindering the quantitative determination of the drug release pattern from the conventional UV-Vis absorption technique. In this article, we report the use of an original synchrotron radiation calibration method based on the combination of XAS and UV-Vis for the quantitative determination of the amount of Pt-based molecules released in water. Thanks to the combination of UV-Vis, XAS and Raman techniques, we demonstrated that both the CisPt molecules and the CisPt-derived species are loaded into an ureasil-PPO/ureasil-poly(ethylene oxide) (PEO) hybrid blend matrix. The experimentally determined molar extinction coefficient of the CisPt-derived species loaded into ureasil-PPO hybrid matrix enabled the simultaneous time-resolved monitoring of each Pt species released from this hybrid blend matrix.

Effect of cerium on structure modifications of a hybrid sol-gel coating, its mechanical properties and anti-corrosion behavior

An organic-inorganic hybrid coating was developed to improve the corrosion resistance of the aluminum alloy AA 2024-T3. Organic and inorganic coatings derived from glycidoxypropyltrimethoxysilane (GPTMS) and aluminum tri-sec-butoxide Al((OBu)-Bu-s)(3), with different cerium contents, were deposited onto aluminum by dip-coating process. Corrosion resistance and mechanical properties were investigated by electrochemical impedance measurements and nano-indentation respectively. An optimal cerium concentration of 0.01 M was evidenced. To correlate and explain the hybrid coating performances in relation to the cerium content, NMR experiments were performed. It has been shown that when the cerium concentration in the hybrid is higher than 0.01 M there are important modifications in the hybrid structure that account for the mechanical properties and anti-corrosion behavior of the sol-gel coating. (C) 2012 Elsevier Ltd. All rights reserved.

Electric characterization of a hybrid composite based on POMA/P(VDF- TrFE)/Zn2SiO4 : Mn using impedance spectroscopy

Understanding the microscopic origin of the dielectric properties of disordered materials has been a challenge for many years, especially in the case of samples with more than one phase. For polar dielectrics, for instance, the Lepienski approach has indicated that the random free energy barrier model of Dyre must be extended. Here we analyse the dielectric properties of a polymer blend made up with the semiconducting poly(o-methoxyaniline) and poly( vinylidene fluoride-trifluorethylene) POMA/P(VDF-TrFE), and of a hybrid composite of POMA/P(VDF-TrFE)/Zn2SiO4:Mn. For the blend, the Lepienski model, which takes into account the rotation or stretching of electric dipoles, provided excellent fitting to the ac impedance data. Because two phases had to be assumed for the hybrid composite, we had to extend the Lepienski model to fit the data, by incorporating a second transport mechanism. The two mechanisms were associated with the electronic transport in the polymeric matrix and with transport at the interfaces between Zn2SiO4: Mn microparticles and the polymeric matrix, with the relative importance of the interfacial component increasing with the percentage of Zn2SiO4: Mn in the composite. The analysis of impedance data at various temperatures led to a prediction of the theoretical model of a change in morphology at 190 +/- 40 K, and this was confirmed experimentally with a differential scanning calorimetry experiment.

Siloxane-polypropyleneoxide hybrid ormolytes: structure-ionic conductivity relationships

Siloxane-polypropyleneoxide (PPO) hybrids doped with sodium perchlorate (NaClO4) obtained by the sol-gel process were prepared with two PPO molecular weights (2000 and 4000 g/mol) and two sodium concentrations such as [O]/[Na] = 4 and 15 (O being the ether-type oxygen of PPO chains). The structure of these hybrids was investigated by Na-23 nuclear magnetic resonance (NMR) and X-ray absorption spectroscopy at the sodium K-edge (1071.8 eV) whereas complex impedance spectroscopy was used to determine their ionic conductivity. Three sodium sites were determined by NMR. The conjunction of NMR and X-ray absorption results allows us to identify one site in which Na is in a NaCl structure, a second one in which Na is in contact with perchlorate anions. The third site is attributed to mobile sodium species in interaction with the polymeric chain. The relative proportion of the different sites in the materials determines the ionic conductivity of the materials at room temperature: the largest ionic conductivity is 8.9 x 10(-6) Omega(-1) cm(-1) and is observed on the material with the larger amount (at least 85%) of sites in which sodium interacts with the polymer. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Effectiveness of surface protection for resin-modified glass-ionomer materials

Objective: the purpose of this study was to evaluate the effectiveness of various surface treatments for resin-modified glass-ionomer restorative materials by determining dye uptake spectrophotometrically. Method and materials: Two hundred twenty-four specimens, 4.1 mm in diameter and 2.0 mm thick, were made of 3 materials: Vitremer, Fuji II LC, and Photac-Fil Aplicap. Specimens were divided into 15 groups. The positive and negative control specimens remained unprotected, while the experimental specimens were protected with Heliobond light-activated bonding resin, Colorama nail varnish, or surface coatings indicated by the manufacturers of the glass-ionomer materials. Finishing Gloss for Vitremer, Fuji Varnish for Fuji II LC, and Ketac Glaze for Photac-Fil. The disks were immersed in 0.05% methylene blue for 24 hours except for the negative control group, which was immersed in deionized water. After 24 hours, the disks were removed, washed, and individually placed in 1 mL of 65% nitric acid for 24 hours. The solutions were centrifuged and the spectrophotometric absorbance was determined at 606 nm. The dye uptake was expressed in micrograms of dye per milliliter, and the results were analyzed with the Kruskal-Wallis test. Results: There were no differences in dye uptake among the 3 resin-modified glass-ionomer restorative materials, however, all of them required surface protection. Conclusion: the best surface protection for the 3 evaluated materials was obtained with Heliobond light-activated bonding resin.

Synthesis and electrical characterization of tungsten doped Pb(Zr0.53Ti0.47)O-3 ceramics obtained from a hybrid process

Pure and W-doped PZT ceramics (PZT and PZTW) were prepared by a hybrid process consisting in the association of polymeric precursor and partial oxalate methods. The phase formation was investigated by simultaneous thermal analysis (TG/DSC) and X-ray diffraction (XRD). The effect of W doping PZT and their electrical properties was evaluated. Substitution of W by Ti leads to an increase of Curie temperature and broadening of dielectric constant. A typical hysteresis loop was observed at room temperature and the remnant polarization was increased with the content of W. (c) 2007 Elsevier B.V. All rights reserved.

Synthesis and some properties of hybrid gels of titanium oxide containing europium (III)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Mechanical behaviour of self-compacting concrete with hybrid fibre reinforcement

In this study, fibre-reinforced self-compacting concretes were developed for precast building components, incorporating either adherent metal fibres or polymeric synthetic slipping fibres or a combination of both. To achieve the warranted workability, compressive and splitting tensile strengths, compositions were determined by preliminary tests on self-compacting materials with various proportions of metal fibres. Bending tests in controlled deflection confirmed the positive contribution of fibres in the mechanical behaviour of self-compacting concrete. The comparison between vibrated and self-compacting concretes of similar mechanical characteristics indicated a possible better fibre-matrix bond in the case of self-compacting types. The results also showed that the properties of the hybrid fibre-reinforced self-compacting concrete could be inferred from the properties of the individual single-fibre reinforcements and their respective proportions through simple mix-rules.

Multi-scale structural description of siloxane-PPO hybrid ionic conductors doped by sodium salts

Alkaline metal doped organic - inorganic hybrids have potential applications in the field of portable energy sources. Attractive sol - gel derived urea cross-linked polyether, siloxane - PPO ( poly( propylene oxide)) hybrids doped with sodium salts ( NaClO4 and NaBF4) were examined by multi-spectroscopic approach that includes complex impedance, X-ray powder diffraction (XRPD), small angle X-ray scattering (SAXS), Si-29 and Na-23 magic-angle spinning nuclear magnetic resonance (NMR/MAS), Na K-edge X-ray absorption near edge structure (XANES) and Raman spectroscopies. The goals of this work were to determine which cation coordinating site of the host matrix ( ether oxygen atoms or carbonyl oxygen atoms) is active in each of the materials analyzed, its influence on the nanostructure of the samples and its relation with the thermal and electrical properties. The main conclusion derived from this study is that the NaBF4 salt has a much lower solubility in the hybrid matrix than the NaClO4 salt. Furthermore, the addition of a large amount of salt plays a major role in the hybrid nanostructure and electrical properties, modifying the PPO chain conformation, weakening or breaking the hydrogen bond of the polyether - urea associations and changing the polycondensation and aggregation processes involving the siloxane species.