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Positronium Annihilation Study of Porosity in Silica Xerogels Prepared by a Sol–Gel Process
Author(s) -
Wakabayashi Yuki,
Ito Kenji,
Li HongLing,
Ujihira Yusuke,
Kamitani Kazuya,
Inoue Hiroyuki,
Makishima Akio
Publication year - 2003
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2003.tb03529.x
Subject(s) - physisorption , positronium , nanopore , mesoporous material , materials science , porosity , sodium silicate , sol gel , chemical engineering , boehmite , sodium hydroxide , catalysis , specific surface area , positron annihilation , granulation , analytical chemistry (journal) , chemistry , nanotechnology , positron , composite material , chromatography , organic chemistry , aluminium , physics , quantum mechanics , engineering , electron
Nano‐ and mesopores of bulk silica xerogels were studied by means of positron annihilation lifetime measurement as well as nitrogen physisorption. Effects of an alkaline catalyst concentration in the sol–gel process on the pore sizes and specific surface area were investigated. The pore size was estimated from the ortho ‐positronium lifetime. Remarkable structural changes were found around a relative alkaline concentration of 10 −4 (a molar ratio of sodium hydroxide to tetramethyl ortho ‐silicate). Above this particular catalyst concentration, the nanopore radius decreased from 0.45 to 0.35 nm, whereas the mesopore radius increased from 1 to 8 nm. The positron annihilation lifetime technique was effective in the evaluation of the nano‐ and mesoscopic structural changes of silica xerogel.