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Small‐angle X‐ray scattering and nitrogen adsorption study of the nanoporosity elimination in TEOS sonohydrolysis‐derived xerogels
Author(s) -
Vollet D. R.,
de Castro W. C.,
Donatti D. A.,
Ibañez Ruiz A.
Publication year - 2005
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200406929
Subject(s) - small angle x ray scattering , nanopore , adsorption , materials science , chemical engineering , scattering , nitrogen , siloxane , specific surface area , sol gel , hydrolysis , porosity , analytical chemistry (journal) , chemistry , nanotechnology , composite material , catalysis , chromatography , organic chemistry , optics , physics , engineering , polymer
Small‐angle X‐ray scattering (SAXS) and nitrogen adsorption techniques were used to study the temperature and time structural evolution of the nanoporosity in silica xerogels prepared from acid‐ and ultrasound‐catalyzed hydrolysis of tetraethoxysilane (TEOS). Silica xerogels present a structure of nanopores of fully random shape, size, and distribution, which can be described by an exponential correlation function γ ( r ) = exp (– r / a ), where a is the correlation distance, as predicted by the Debye, Anderson, and Brumberger (DAB) model. The mean pore size was evaluated as about 1.25 nm from SAXS and about 1.9 nm from nitrogen adsorption. The nanopore elimination in TEOS sonohydrolysis‐derived silica xerogels is readily accelerated at temperatures around 900 °C probably by the action of a viscous flow mechanism. The nanopore elimination process takes place in such a way that the pore volume fraction and the specific surface are reduced while the mean pore size remains constant. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)