Shrinkage and Swelling of Alkoxide Silica Gels on Heating, Part II.

Shrinkage and swelling of two series of alkoxide-derived gels were studied. It was confirmed that fluoride ions universally reduce or eliminate swelling by substitution of F sup - for OH sup - on the gel surface. Gels with higher low-temperature shrinkage are less vulnerable to swelling than gels with lower low-temperature shrinkage.