T. Arantes - Academia.edu (original) (raw)

Papers by T. Arantes

Journal of Colloid and Interface Science, 2016

Distinct affinities between the organic and inorganic phases were observed in nanocomposites prep... more Distinct affinities between the organic and inorganic phases were observed in nanocomposites prepared through a colloidal route with carboxylated nitrile rubber and modified silica nanoparticles, which resulted in variable mechanical properties and improved thermal stability. Nanoparticles with modified surface affected the macromolecular arrangements of the elastomeric matrix, changing the final mechanical behavior of the nanocomposite, which could be predicted by the spin-lattice relaxation time measured by solid-state NMR. It was also possible to identify how each different nanoparticle affected the molecular dynamic of nanocomposite, correlating the dynamic-mechanical analysis with the NMR data of the saturated carbons of the elastomer.

Materials Science Forum, 2014

The purpose of this work is to study the structural and morphological modification of the surface... more The purpose of this work is to study the structural and morphological modification of the surface of the n-type diamond electrodes as a function of nitrogen doping. The characterizations of these electrodes were made using Raman Spectroscopy, Contact Angle, X-ray diffraction and Scanning Electron Microscopy (SEM). The nitrogen-doped diamond (NDD) electrodes were produced using Hot Filament-assisted Chemical Vapor Deposition method (HFCVD) from methane, hydrogen and nitrogen in the gas mixture. The results from Raman spectroscopy show that the diamond films obtained with nitrogen addition presented one large band at 1100-1700 cm-1. The SEM images showed that the variation in the nitrogen doping influenced the growth rate of films by promoting changes in the sizes of grains from microcrystalline to nanocrystalline texture. This behavior supported the results obtained from X-ray diffraction analyses. It was possible to verify a decrease in the crystallite size as a function of the nitr...

Química Nova, 2007

Recebido em 11/10/05; aceito em 31/5/06; publicado na web em 28/11/06 OBTAINING COPPER SELENIDE T... more Recebido em 11/10/05; aceito em 31/5/06; publicado na web em 28/11/06 OBTAINING COPPER SELENIDE THICK FILMS ON VITREOUS CARBON, GOLD, TITANIUM AND COPPER. Copper selenide (berzelianite) films were prepared on the title substrates using the chemical bath deposition technique (CBD). Film composition was determined by energy dispersion of x-rays. The kinetics of film growth is parabolic and film adherence limits the film thickness. On titanium, copper selenide forms islands that do not completely cover the surface, unless the substrate is prepared with a tin oxide layer; film composition also depends on the titanium oxide layer. On vitreous carbon, CBD and mechanical immobilization techniques lead to films with similar resistances for the electron transfer across the film/substrate interface. On gold, composition studies revealed that film composition is always the same if the pH is in the range from 8 to 12, in contrast to films prepared by an ion-ion combination route. On copper, a new procedure for obtaining copper selenide films as thick as 5 μm has been developed.

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014

h i g h l i g h t s • We modified silica nanoparticles with a silane agent and with a polymeric s... more h i g h l i g h t s • We modified silica nanoparticles with a silane agent and with a polymeric shell. • SiO 2 nanoparticles induced arrangements in XNBR nanocomposites. • The SDS induced the polymeric macromolecules organization in the nanocomposites. • The silica nanoparticles dispersed in the polymer forming a mass fractal system. • The silica nanoparticles and XNBR chains formed three-dimensional network.

Polymer Testing, 2009

The chemical behavior of styrene-butadiene rubber (SBR) and of the SBR/TiO 2 and photodegraded SB... more The chemical behavior of styrene-butadiene rubber (SBR) and of the SBR/TiO 2 and photodegraded SBR/TiO 2 nanocomposites was investigated through nuclear magnetic resonance spectroscopy (NMR) in the solid state with magic angle spinning (MAS). The 13 C cross polarization/magic angle spinning (CP/MAS) routine spectrum allowed us to obtain information on the polymer microstructure and also to evaluate the domain mobilities. The variation contact time and the proton spin-lattice relaxation time in the rotating frame (T 1 rH) were determinant factors to evaluate the dynamic molecular motion. The NMR spectrum of the nanocomposites was dislocated 5 ppm to higher chemical shift, indicating the presence of a strong interaction between the polymer chains and the TiO 2 nanoparticles. The VTC experiment showed a rigid domain in the SBR/TiO 2 photodegraded nanocomposite due to cross-linking reactions.

Journal of Applied Polymer Science, 2012

Much has been talking about the advantages of polymeric nanocomposites, but little is known about... more Much has been talking about the advantages of polymeric nanocomposites, but little is known about the influence of nanoparticles on the stability of these materials. In this sense, we studied the influence of both oxides of zirconium and titanium, known to have photocatalytic properties, as well as the influence of synthetic clay Laponite on the photodegradation of styrene-butadiene rubber (SBR). SBR nanocomposites were prepared by the colloidal route by mixing commercial polymer lattices and nanometric anatase TiO 2 , monoclinic ZrO 2 or exfoliated Laponite clays colloidal suspensions. To better understand the degradation mechanisms that occur in these nanocomposites, the efficiency of different photocatalysts under ultraviolet radiation was monitored by FT-IR and UV-vis spectroscopies and by differential scanning calorimetric. It was observed that TiO 2 and ZrO 2 nanoparticles undoubtedly acted as catalysts during the photodegradation process with different efficiencies and rates. However, when compared to pure SBR samples, the polymer degradation mechanism was unaffected. Unlike studies with nanocomposites montmorillonite, exfoliated laponite clay effectively acts as a photostabilizer of polymer UV photodegradation. V

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2012

Journal of Nanoparticle Research, 2010

Nanocrystalline zirconium oxide was synthesized by hydrothermal treatment of ZrO(NO 3) 2 and ZrOC... more Nanocrystalline zirconium oxide was synthesized by hydrothermal treatment of ZrO(NO 3) 2 and ZrOCl 2 aqueous solutions at different temperatures and time in presence of hydrogen peroxide. Hydrothermal treatment of zirconium salts (0.25 and 0.50 mol L-1) produced nanocrystalline monoclinic ZrO 2 powders with narrow size distribution, which were formed by the attachment of the smaller particles with crystallites size of 3.5 nm, estimated by means of the Scherrer's equation and confirmed by transmission electronic microscopy. Typical monoclinic zirconium oxide X-ray powder diffraction patterns and Raman spectra were obtained for all the crystalline powders. It was observed that the crystallization depends strongly on the temperature, resulting in amorphous material when the synthesis was realized at 100°C, and crystalline with monoclinic phase when synthesized at 110°C, independently of the salt used. Zirconium oxide colloidal nanoparticles were formed only at hydrothermal treatments longer than 24 h. The stability of the colloids was successfully characterized of zeta potential, showing an initial value of ? 59.2 mV in acid media and isoelectric point at pH = 5.2, in good agreement with previous studies.

Journal of Applied Polymer Science, 2009

The synthesis of colloidal SiO2 nanoparticles was achieved via the base-catalyzed hydrolysis and ... more The synthesis of colloidal SiO2 nanoparticles was achieved via the base-catalyzed hydrolysis and polycondensation
of tetraethyl orthosilicate (TEOS) in an alcoholic medium with the careful variation of the
concentrations of water, ammonia and TEOS. In this study, we investigated the influence of experimental
parameters on the average size of nanoparticles by means of a multivariate statistical analysis using a
factorial design to create one model to predict particle size in function of experimental conditions. This
model predicted that it is possible to synthesize silica nanoparticles with size in the range from 17 to
333 nm, according to the chosen condition for the amount of water, ammonia and TEOS. It was observed
that only the molar amount of NH3, the molar amount of H2O and the effect from interaction between
molar amount of TEOS and H2O were significant. Subsequently, surface modification of the colloidal silica
was performed in situ using the coupling agent 3(trimethoxysilyl)propyl methacrylate (TMSPM).

The chemical behavior of styrene-butadiene rubber (SBR) and of the SBR/TiO2 and photodegraded SBR... more The chemical behavior of styrene-butadiene rubber (SBR) and of the SBR/TiO2 and photodegraded
SBR/TiO2 nanocomposites was investigated through nuclear magnetic resonance
spectroscopy (NMR) in the solid state with magic angle spinning (MAS). The 13C
cross polarization/magic angle spinning (CP/MAS) routine spectrum allowed us to obtain
information on the polymer microstructure and also to evaluate the domain mobilities.
The variation contact time and the proton spin-lattice relaxation time in the rotating frame
(T1rH) were determinant factors to evaluate the dynamic molecular motion. The NMR
spectrum of the nanocomposites was dislocated 5 ppm to higher chemical shift, indicating
the presence of a strong interaction between the polymer chains and the TiO2 nanoparticles.
The VTC experiment showed a rigid domain in the SBR/TiO2 photodegraded
nanocomposite due to cross-linking reactions.