Published online by Cambridge University Press: 21 February 2011
Sols were prepared in the system TMOS:H2O:SOLV:HC1 with molarratios of 1:4:3:0.0005 for SOLV = MeOH, EtOH and DMF. The gelation and agingof these sols took place in cuvettes covered by parafilm. The gels wereremoved from the cuvettes 14 days after gelation. Solvent exchange wascarried out in each of the three solvents for a period of 14 days. Startingwith fresh solvent, the exchange was repeated three times.
TGA and DTA curves were taken with pieces of the original gels and of gelsafter the 2nd and 3rd solvent exchange. The TGA curves display aconsiderable weight loss in the temperature range of solvent evaporation. Asmall step is observed at higher temperatures if MeOH or EtOH represent theexchange solvent. The DTA curves allow a distinction what mixtures ofsolvents are present. The effectiveness of the solvent exchange can beevaluated.