TY - JOUR
T1 - Microstructure and porosity of silica xerogel monoliths prepared by the fast sol-gel method
AU - Bryans, Tracy R.
AU - Brawner, Vikki L.
AU - Quitevis, Edward L.
N1 - Funding Information:
This work was supported by grants from the State of Texas through the Advanced Research Program (003644-057) and the Robert A. Welch Foundation (D-1019). We thank Professor D. Casadonte for the use of the NOVA 1000 in carrying out the BET measurements and M. Grimson of the Electron Microscopy Laboratory at Texas Tech University for carrying out the SEM measurements.
PY - 2000
Y1 - 2000
N2 - An adaptation of the fast sol-gel method to the synthesis of xerogel monoliths using tetramethoxysilane (TMOS) as the alkoxide precursor is described in this paper. The procedure involves running the reaction at 70-80 °C in an open vessel, which accelerates hydrolysis and condensation and reduces the amount of liquid by expelling excess methanol throughout distillation. This procedure yields crack-free monoliths. The porosity and microstructure of these xerogel monoliths were studied by using N2 adsorption and desorption and scanning electron microscopy (SEM). The SEM data show that the solid skeletal phase has a globular morphology with particles, 20-40 nm in diameter, arranged into agglomerates a few hundred nm in diameter. The microstructure of the acid-catalyzed xerogel is a consolidation of these agglomerates. The isotherm data show these xerogels to be microporous. In contrast, the base-catalyzed xerogel has a hierarchical morphology with the clusters of agglomerates organized into larger clusters approaching 1 μm in diameter. An analysis of the isotherm data shows these xerogels to be less microporous with a narrow distribution of mesopores having an average diameter of 50 angstroms.
AB - An adaptation of the fast sol-gel method to the synthesis of xerogel monoliths using tetramethoxysilane (TMOS) as the alkoxide precursor is described in this paper. The procedure involves running the reaction at 70-80 °C in an open vessel, which accelerates hydrolysis and condensation and reduces the amount of liquid by expelling excess methanol throughout distillation. This procedure yields crack-free monoliths. The porosity and microstructure of these xerogel monoliths were studied by using N2 adsorption and desorption and scanning electron microscopy (SEM). The SEM data show that the solid skeletal phase has a globular morphology with particles, 20-40 nm in diameter, arranged into agglomerates a few hundred nm in diameter. The microstructure of the acid-catalyzed xerogel is a consolidation of these agglomerates. The isotherm data show these xerogels to be microporous. In contrast, the base-catalyzed xerogel has a hierarchical morphology with the clusters of agglomerates organized into larger clusters approaching 1 μm in diameter. An analysis of the isotherm data shows these xerogels to be less microporous with a narrow distribution of mesopores having an average diameter of 50 angstroms.
UR - http://www.scopus.com/inward/record.url?scp=0033889084&partnerID=8YFLogxK
U2 - 10.1023/A:1008711921746
DO - 10.1023/A:1008711921746
M3 - Article
AN - SCOPUS:0033889084
VL - 17
SP - 211
EP - 217
JO - Journal of Sol-Gel Science and Technology
JF - Journal of Sol-Gel Science and Technology
SN - 0928-0707
IS - 3
ER -