Shrinkage and microstructural development during drying of organically modified silica xerogels
- New Mexico Univ., Albuquerque, NM (United States)
- Nanopore Corp., Albuquerque, NM (United States)
We have studied the different driving forces behind syneresis in MTES/TEOS gels by aging them in different H{sub 2}O/EtOH pore fluids. We show using shrinkage, density, contact angle, and N{sub 2} sorption measurements, the influence of gel/solvent interactions on the microstructural evolution during drying. Competing effects of syneresis (that occurs during aging) and drying shrinkage resulted in the overall linear shrinkage of the organically modified gels to be constant at {approximately}50%. Increasing the hydrophobicity of the gels caused the driving force for syneresis to change from primarily condensation reactions to a combination of condensation and solid/liquid interfacial energy. In addition the condensation driven shrinkage was observed to be irreversible, whereas the interfacial free energy driven shrinkage was observed to be partially reversible. Nitrogen sorption experiments show that xerogels with the same overall extent of shrinkage can have vastly different microstructures due to the effects of microphase separation.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States); Electric Power Research Inst., Palo Alto, CA (United States); National Science Foundation, Washington, DC (United States); Gas Research Inst., Chicago, IL (United States); New Mexico Univ., Albuquerque, NM (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 254233
- Report Number(s):
- SAND--96-1482C; CONF-960401--56; ON: DE96011698
- Country of Publication:
- United States
- Language:
- English
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