Results 141 to 150 of about 2,730 (185)

Low-frequency dynamics in silica xerogels

Journal of Physics: Condensed Matter, 1996
Brillouin and Raman experiments have been performed in hydrogenated silica sol - gel and vitreous silica samples made by sol - gel processes (xerogels) and by the melting powder method. The aim of this work has been the study of the low-frequency dynamics of sol - gel systems in comparison with that of amorphous silica.
Fontana, Aldo, E. Moser, F. Rossi, Campostrini, Renzo, Carturan, Giovanni   +4 more
openaire   +2 more sources

The Structure of Confined Oxygen in Silica Xerogels

Science, 1995
The microscopic structure of oxygen confined in silica xerogels has been studied as a function of temperature. In large pores, a crystalline solid forms with a structure consistent with that of the bulk. The size of the crystallites is much larger than the pore size, indicating that cooperative effects among pores are ...
B S, Schirato, M P, Fang, P E, Sokol, S, Komarneni   +3 more
openaire   +2 more sources

Preparation of Aerogel and Xerogel Nanocomposite Materials

MRS Proceedings, 1999
ABSTRACTSol-gel method was used to prepare nickel oxide-silica and iron oxide-silica nanocomposites materials in form of aerogels and xerogels. The samples were characterized by thermal analysis, X-ray diffraction, N2 physisorption and transmission electron microscopy techniques.
CASULA, MARIA FRANCESCA, CORRIAS, ANNA, Paschina G.   +2 more
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Structure of Hybrid Colloid−Polymer Xerogels

Langmuir, 2004
Crack-free monolithic gels were prepared from different mixtures of colloidal silica with a sol solution containing tetraethoxysilane, under powerful ultrasonic agitation (sonosol). Recently, information on the structure of these gels, inferred from N2 adsorption and mercury intrusion porosimetry, was presented.
Luis, Esquivias, Nicolás, de la Rosa-Fox, Mercedes, Bejarano, Maria J, Mosquera   +3 more
openaire   +2 more sources

Antenna effect in an oxide xerogel

Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy, 1998
Abstract Silica xerogel doped with [Eu⊂cryptand] 3+ was prepared by the sol-gel method from a hydrolyzed tetramethoxysilane solution containing [Eu⊂cryptand](CF 3 SO 3 ) 2 Br. UV-visible optical absorption spectra, fluorescence excitation and emission spectra, fluorescence lifetime as well as luminescence quantum yield were measured. Experiments were
Marek Pietraszkiewicz, Stefan Lis, Zbigniew Hnatejko   +2 more
exaly   +2 more sources

Carbon xerogels as catalyst supports: Study of mass transfer

AIChE Journal, 2006
AbstractHydrodechlorination of 1,2‐dichloroethane on Pd‐Ag alloys was used as a test reaction in order to study mass transfer in carbon xerogel supports. The selected supports were obtained from evaporative drying and pyrolysis of resorcinol‐formaldehyde aqueous gels. Since the pore texture of these materials can be tailored through the adequate choice
Job, Nathalie, Heinrichs, Benoît, Lambert, Stéphanie, Pirard, Jean-Paul, Colomer, Jean-François, Vertruyen, Bénédicte, Marien, José   +6 more
openaire   +1 more source

Low-Energy Vibration Excess in Silica Xerogels

Physical Review Letters, 1997
Specific heat (1.5-25 K) and Raman scattering (below 100cm −1 in silica xerogels permit one to assess the frequency dependence of the coupling coefficient C(ω)and the low-energy density of states g(ω) Different network connectivity does not change the shape of the quasielastic scattering, but alters the spectral shape of C(ω)The results permit one to ...
FONTANA A, ROSSI F, CARINI, Giuseppe, D'ANGELO, Giovanna, TRIPODO, Gaspare, BARTOLOTTA A.   +5 more
openaire   +4 more sources

Carbon Xerogels for Effluent Treatment

Journal of Chemical & Engineering Data, 2020
The adsorption process of carbonized xerogels in the form of porous microspheres or monoliths was found to be reversible.
Athulya Pillai, Balasubramanian Kandasubramanian   +1 more
openaire   +1 more source

Aerogels and xerogels for catalytic applications

Journal of Non-Crystalline Solids, 1992
Abstract The aerogel method, consisting of preparation of solid catalysts by sol-gel processes of organometallic precursors and drying the wet gel under hypercritical conditions, is a particularly interesting way to obtain highly divided materials for catalytic applications. Special attention is given to PbO ZrO 2 and PbO Al 2 O 3 aerogel catalysts.
R. Tleimat-Manzalji, T. Manzalji, G.M. Pajonk   +2 more
openaire   +1 more source

Elastic Properties of Silica Xerogels

Journal of the American Ceramic Society, 1990
To calculate elastic constants, longitudinal and tranverse acoustic wave velocities were measured for silica xerogels as a function of relative humidity (rh). The silica xerogels studied are microporous with open porosity of 53 vol%. The longitudinal wave velocity exhibits a minimum at about 35% rh.
Bennet Abramoff, Lisa C. Klein
openaire   +1 more source