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317 results on '"Mariotto, Gino"'

102. Determination of nanosized particles distribution by low frequency Raman scattering: Comparison to electron microscopy

Author

Ivanda, Mile, Tonejc, Anđelka, Djerdj, Igor, Gotić, Marijan, Musić, Svetozar, Mariotto, Gino, Montagna, Maurizio, Watanabe, Y., Heun, S., Salviati, G., and Yamamoto, N.

Subjects
Ramanovo raspršenje, nanokristali, visoko rezolucijska transmisijska elektronska mikroskopija, distribucija čestica po veličini
Abstract

The methodology for the determination of nanosized particle distribution by low frequency Raman spectroscopy is described. It is based on w-1 dependence of the Raman light to vibration coupling coefficient and on the fact that each nanocrystallite of diameter D vibrates with its eigen frequency w~1/D. The effect of the particle vibrational lifetime on the shape of distribution is analyzed and found to be negligible for the free TiO2 nanoparticles. The size distributions of TiO2 nanoparticles estimated by Raman spectroscopy was compared with those of transmission electron microscopy including dark field and high resolution imaging. The Raman spectroscopy showed to be simple, fast method that has favourable statistic over the macroscopic probe volume and makes possible ''in situ'' measurements.

Published
2002

104. Raman light-to-vibration coupling coefficient of v-SiO2 in spectral interval range up to 600 cm(-1)

Author

Ivanda, Mile, Kiefer, Wolfgang, and Mariotto, Gino

Subjects
Phonons. Order-disorder effects. Neutron scattering. Inelastic light scattering
Abstract

Raman and inelastic neutron spectra of vitreous silica were compared in order to derive the Raman light-to-vibration coupling coefficient C(v) in the spectral interval between 10 and 600 cm(-1). C(v) shows different frequency dependences in different spectral regions: between 30 and 110 cm(-1), C(v) proportional to v; between 110 and 450 cm(-1), C(v) is constant; and finally, between 450 and 550 cm(-1), C(v) sharply decreases. The results are discussed in the frame of the existing models for the vibrational excitations in vitreous silica. The crossover frequency of C(v) at similar to 110 cm(-1) is interpreted as the onset of phonon localization in the sense of Ioffe-Regel rule.

Published
2001

105. Comparison of high resolution transmission electron microscopy and low frequency Raman scattering in determination of particles size distribution of nanosized TiO2

Author

Ivanda, Mile (predavač), Tonejc, Anđelka M., Djerdj, Igor, Gotić, Marijan, Musić, Svetozar, Mariotto, Gino, and Heun, Stefano

Subjects
TiO2 nanoparticles, size distribution, Raman scattering
Abstract

Size distribution of TiO2 nanoparticles synthesized by sol-gel method are determined by high resolution transmission electron microscopy (HRTEM) and compared with those determined by low frequency Raman scattering (LFRS). The methodology for the determination of nanosized particle distribution by LFRS is described. It is based on n-1 dependence of the Raman light to vibration coupling coefficient and on the fact that each nanocrystallite of diameter D vibrates with its own eigen frequency n~1/D. The effect of the particle vibrational lifetime on the shape of distribution is analyzed and found to be negligible for the weakly connected TiO2 particles. Fig. 1 shows comparison of the HRTEM and LFRS TiO2 size distributions. On the basis of comparison of particle size distributions deduced by HRTEM and LFRS on 15 different samples, the Raman spectroscopy shows to be simple, fast method that has favorable statistic over the macroscopic probe volume and that enables ''in situ'' measurements.

Published
2000

107. Vibrational Density of States and Elastic Properties of Cross-Linked Polymers: Combining Inelastic Light and Neutron Scattering

Author

Crupi, Vincenza, primary, Fontana, Aldo, additional, Giarola, Marco, additional, Longeville, Stéphane, additional, Majolino, Domenico, additional, Mariotto, Gino, additional, Mele, Andrea, additional, Paciaroni, Alessandro, additional, Rossi, Barbara, additional, Trotta, Francesco, additional, and Venuti, Valentina, additional

Published
2014
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112. Cyclodextrin-Complexation Effects on the Low-Frequency Vibrational Dynamics of Ibuprofen by Combined Inelastic Light and Neutron Scattering Experiments

Author

Crupi, Vincenza, primary, Fontana, Aldo, additional, Giarola, Marco, additional, Guella, Graziano, additional, Majolino, Domenico, additional, Mancini, Ines, additional, Mariotto, Gino, additional, Paciaroni, Alessandro, additional, Rossi, Barbara, additional, and Venuti, Valentina, additional

Published
2013
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114. Enhancement of proton mobility and mitigation of methanol crossover in sPEEK fuel cells by an organically modified titania nanofiller.

Author

Bonis, Catia, Simari, Cataldo, Kosma, Vasiliki, Mecheri, Barbara, D'epifanio, Alessandra, Allodi, Valentina, Mariotto, Gino, Brutti, Sergio, Suarez, Sophia, Pilar, Kartik, Greenbaum, Steve, Licoccia, Silvia, and Nicotera, Isabella

Subjects
PROTON mobility, METHANOL, NANOCOMPOSITE materials, FUEL cells, TITANIUM dioxide
Abstract

An organically functionalized titania, TiO-RSOH, was evaluated as filler in sulfonated polyetheretherketone (sPEEK)-based composite membranes for application in high temperature direct methanol fuel cells. The presence of propylsulfonic acid groups covalently bound onto the TiO surface and the nanometric nature of the additive were analyzed by Raman spectroscopy and transmission electron microscopy, respectively. The properties of the sPEEK/TiO-RSOH composite membranes were compared with those of the pure sPEEK membranes and those of the sPEEK/TiO composite membranes containing pristine titania nanoparticles at same filler content. Water and methanol transport properties were investigated by NMR methods, including relaxation times and self-diffusion coefficients as function of temperature (up to 130 °C), and pressure (from 0 up to 2 kbar). The incorporation of the nanoadditivies in the sPEEK polymer demonstrates considerable effects on the morphology and stiffness of the membranes, as well as on the transport properties and barrier effect to the methanol crossover. In particular, the functionalization by propylsulfonic acid groups promotes a higher reticulation between the polymeric chains, increasing the tortuosity of the methanol diffusional paths, so reducing the molecular diffusion, while the proton mobility increases being favored by the Grotthus-type mechanism. Conductivity measurements point out that the filler surface functionalization avoids the reduction of the overall proton conduction of the electrolyte due to the embedding of the low-conducting TiO. Finally, remarkable improvements were found when using the sPEEK/TiO-RSOH composite membrane as electrolyte in a DMFC, in terms of reduced methanol crossover and higher current and power density delivered. [ABSTRACT FROM AUTHOR]

Published
2016
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115. Structural and Spectroscopic Characterization of A Nanosized Sulfated TiO2 Filler and of Nanocomposite Nafion Membranes.

Author

Allodi, Valentina, Brutti, Sergio, Giarola, Marco, Sgambetterra, Mirko, Navarra, Maria Assunta, Panero, Stefania, and Mariotto, Gino

Subjects
NANOCOMPOSITE materials spectra, TITANIUM dioxide nanoparticles, NAFION, FILLER materials, X-ray diffraction, SULFATES, THERMOGRAVIMETRY, TRANSMISSION electron microscopy
Abstract

A large number of nano-sized oxides have been studied in the literature as fillers for polymeric membranes, such as Nafion®. Superacidic sulfated oxides have been proposed and characterized. Once incorporated into polymer matrices, their beneficial effect on peculiar membrane properties has been demonstrated. The alteration of physical-chemical properties of composite membranes has roots in the intermolecular interaction between the inorganic filler surface groups and the polymer chains. In the attempt to tackle this fundamental issue, here we discuss, by a multi-technique approach, the properties of a nanosized sulfated titania material as a candidate filler for Nafion membranes. The results of a systematic study carried out by synchrotron X-ray diffraction, transmission electron microscopy, thermogravimetry, Raman and infrared spectroscopies are presented and discussed to get novel insights about the structural features, molecular properties, and morphological characteristics of sulphated TiO2 nanopowders and composite Nafion membranes containing different amount of sulfated TiO2 nanoparticles (2%, 5%, 7% w/w). [ABSTRACT FROM AUTHOR]

Published
2016
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116. Nitrogen implantation into amorphous carbon films: sims and positron annihilation analyses

Author

Freire Junior, Fernando Leite, Franceschini, Dante F., Achete, Carlos A., Baumvol, Israel Jacob Rabin, Brusa, R.S., Mariotto, Gino, and Canteri, R.

Subjects
Física da matéria condensada, Filmes finos, Implantação de íons
Abstract

Hard amorphous hydrogenated carbon films deposited by self-bias glow discharge were implanted at room temperature with 70 keV-nitrogen ions at fluences between 2.0 and 9.0 x 10 16 N/cm2. The implantation energy was chosen so that the projected range plus range straggling (Rp+∆Rp) was smaller than the film thickness. The implanted samples were analyzed by Raman scattering, Secondary ion mass spectrometry (SIMS) and positron annihilation spectroscopy, using the Doppler broadening technique with the determination of the shape parameter (S parameter). Depth profiles of implanted species agree well with the predictions of the Monte Carlo code, Transport of Ions in Matter (TRIM-90). For samples implanted with 2 x 1016 N/cm2 the S parameter follows the vacancies depth profile predicted by the simulation. For higher fluences we observed a reduction in the measured value of S. The first result was interpreted as being due to the point defects generated during the ion stopping, whereas the PAS results for higher fluences were due to the structural modifications (increase of disorder and of the number, or size, of the graphitic domains) induced in the carbon films by the incident ions combined with the point defects generated by the atomic collisions.

Published
1996

121. STUDIES OF MERCURATED DERIVATIVES OF ACETYLACETONE AND ETHYL ACETOACETATE BY SOLID-STATE NUCLEAR-MAGNETIC-RESONANCE AND VIBRATIONAL SPECTROSCOPIES

Author

Bonhomme, C., Maquet, J., Livage, J., and Mariotto, Gino

Subjects
VIBRATIONAL SPECTROSCOPY (RAMAN), MERCURATED DERIVATIVES OF ACETYLACETONE AND ETHYL ACETOACETATE, MERCURATED DERIVATIVES OF ACETYLACETONE AND ETHYL ACETOACETATE, SOLID-STATE NUCLEAR-MAGNETIC-RESONANCE (NMR-MAS), SOLID-STATE NUCLEAR-MAGNETIC-RESONANCE (NMR-MAS)
Published
1995

123. OPTICAL AND MAGNETIC INVESTIGATIONS OF NA+/PR3+-BETA'-AL2O3

Author

Tietz, F., Zanghellini, E., Mariotto, Gino, Dedecke, T., and Urland, W.

Subjects
BETA''-ALUMINA, OPPTICAL SPECTROSCOPY, BETA''-ALUMINA, Pr3+-ION, OPPTICAL SPECTROSCOPY, MAGNETIC SUSCEPTIBILITY, MAGNETIC SUSCEPTIBILITY, Pr3+-ION
Published
1995

131. IN-DEPTH MODIFICATIONS OF IMPLANTED AMORPHOUS-CARBON FILMS

Author

Freire, F. L., Achete, C. A., Franceschini, D. F., and Mariotto, Gino

Subjects
RAMAN DEPTH-PROFILE, AMORPHOUS-CARBON FILMS, ION IMPLANTATION, RAMAN DEPTH-PROFILE, ION IMPLANTATION, AMORPHOUS-CARBON FILMS
Published
1994

145. VERY LOW-FREQUENCY LIGHT-SCATTERING IN GLASS MATRIX

Author

Lipinskakalita, K. E. and Mariotto, Gino

Subjects
Raman spectroscopy, Very low frequency light scattering, Raman spectroscopy, Very low frequency light scattering, glass matrix, glass matrix
Published
1992

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