Semiporous monolith

Figure 10.1 Types of silica-based sol-gel monoliths differing in porosity, (a) Aerogels, highly porous monoliths, (b) Xerogel, semiporous monoliths, (c) Inorganic-organic hybrid, nonporous monoliths.

Xerogel monoliths are semiporous monoliths (usually 30-70% porosity). Yoldas [40] in the 1970s was the first to demonstrate fabrication of monoliths via a sol-gel process. Since then numerous routes for fabrication of xerogel silica monoliths and nonsilica monoliths were suggested and demonstrated. In this section a few examples of xerogel monolith febrication will be presented. 

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