Accession Number : ADP007475

Title :   Designing Pore-Size in Silica Gels:H20-TMOS System,

Corporate Author : PENNSYLVANIA STATE UNIV UNIVERSITY PARK MATERIALS RESEARCH LAB

Personal Author(s) : Kido, H. ; Malla, P.B. ; Komareni, S.

Report Date : FEB 1991

Pagination or Media Count : 6

Abstract : A series of microporous silica gels were synthesized by hydrolyzing tetramethylorthosilicate (TMOS) with varying amounts of water. No catalyst or alcohol 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 H20/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 deg C after degassing at 200 deg 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.

Descriptors :   *DIFFERENTIAL THERMAL ANALYSIS, CATALYSTS, GELATION, GELS, ISOTHERMS, MEASUREMENT, NITROGEN, REDUCTION, SHAPE, SILICA GELS, SORPTION, SURFACES, THERMAL ANALYSIS, TIME, VARIATIONS, WATER.

Subject Categories : Statistics and Probability

Distribution Statement : APPROVED FOR PUBLIC RELEASE