Physical-Chemical Variables in Processing Na2O - B2O3 - SiO2 Gel Monoliths

Abstract

ABSTRACTThe addition of a dryinq control chemical additive (DCCA) to the solvent allows short drying times for monolithic gel samples. The variables involved in the use of a DCCA in preparing gels from the Na2O-SiO2 -B2O3 system are described. Due to its higher reactivity, a DCCA influences the chemical behavior of the material at each step of the processing. The effects of formamide as a DCCA on the qelation process, surface charge, and surface area are presented. The variations of the physical properties of the gel, due to the addition of the DCCA, are related to the reactions of the formamide with the sol. Although the DCCA helps in producing monolithic dried gels, the problem of densification is not solved as yet.