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Anomalously Low Surface Area and Density in the Silica—Alumina Gel System
Author(s) -
Hietala Susan L.,
Smith Douglas M.,
Golden Johnny L.,
Brinker C. Jeffrey
Publication year - 1989
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.1151-2916.1989.tb06088.x
Subject(s) - porosity , yield (engineering) , materials science , mineralogy , range (aeronautics) , specific surface area , surface (topology) , bulk density , analytical chemistry (journal) , chemistry , composite material , chromatography , geometry , catalysis , geology , organic chemistry , mathematics , soil science , soil water
A range of composition/processing conditions that yield xerogel surface areas 2 orders of magnitude lower than expected along with low skeletal densities has been discovered. For xerogel compositions in the vicinity of 50 wt% Al 2 O 3 , surface areas are 1 to 5 m 2 /g and skeletal densities are 2.1 to 2.2 g/cm 3 , as compared to the expected values of ∼300 m 2 /g and ∼2.6 g / cm 3 , respectively. This behavior is observed over a wide range of heat treatment temperatures (373 to 1073 K) and appears to be the result of closed porosity which evolves during gel drying.