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Designing Pore-Size in Silica Gels: [H2O] – [TMOS] System

Published online by Cambridge University Press:  21 February 2011

H. Kido ,
P. B. Malla  and
S. Komarneni
H. Kido
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802
P. B. Malla
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802
S. Komarneni
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802
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Abstract

A series of microporous silica gels were synthesized by hydrolyzing tetramethylorthosilicate (TMOS) with varying amounts of water. No catalyst or alcohal was added. The gels were characterized by water sorption isotherms, the BET nitrogen surface area measurements, and differential thermal analysis. Although the gelation time for all H2O/TMOS molar ratios (R) was approximately the same (about 3 hr), the pore-size (pore diameter) and sorption capacity were found to be minimum in the R range 4.96–5.37 but increased with both increasing and decreasing R. Water sorption isotherms measured at 25°C after degassing at 200°C of gels prepared with R = 4.96–5.37 exhibited moderate Type I (Brunauer classification) isotherm which changed to intermediate between Type I and Type IV with decreasing or increasing R. These results indicated that the amount of organic or water which was not utilized in the reaction and the degree of cross-linking apparently played a role for the observed variations in pore-size or shape of water isotherms.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 175: Symposium S – Multifunctional Materials , 1989 , 219
Copyright
Copyright © Materials Research Society 1990

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