Effects of the high pressure on the morphology of silica-based hybrid xerogels

Abstract

The hybrid biphenylaminepropylsilica (bPhe/SiO₂) and biphenylaminepropylsilicatitania xerogels were obtained by the sol-gel synthesis. The bPhe/SiO₂ material showed higher porosity and higher thermal stability of the organic component. These materials were submitted to high-pressure processing (3.5 and 6.0 GPa) and the changes in their morphological properties were investigated by using scanning electron microscopy, N₂ adsorption–desorption isotherms and infrared spectroscopy. The high-pressure processing produces changes in the morphological structure of hybrid materials caused by the compaction of the aggregated particles and the blocking of the pores with the entrapment of organics through the cold sintering process. However, when the organics are covalently bonded to the surface, this mechanism can be partially inhibited.

Keywords:

• Amorphous materials
• Sol-gel chemistry
• Microstructure

Acknowledgements

We thank FAPERGS, CNPq for financial support and grants. We also thank to CME—UFRGS for the use of the SEM.