I'm using TEOS as my precursor with acidic condition. Sample obtained after solidification (simple room temperature drying) of gel is good too. To obtain glass from solidified gel we are heating the sample at certain period of time (let's say 10 hrs - 2-3 days) at certain temperature. I want to basically obtain glass as my final sample with the stability. On heating solidified gel even turns to small pieces along with some dendrite growth (x-ray crystalline). After research survey I even tried to make the samples stabilized by heating them for 20 days at constant temperature. But still the issue persists. And I want to use the samples for conductivity measurements.
For limiting cracks:
- introduce surfactant in the formulation
- heat very very slowly, with constant temperature steps when volatiles are released (the temperatures at which this occurs can be found by thermogravimetry)
- if phase separation occurs, then your formulation is not stable and there is not much to do but preparing a different one.
Alain
Thanks Alain. Can I just get an idea for introducing surfactant into the system and will it not play with the desired composition.
The surfactant must be introduced in the formulation from the very beginning. I used to test commercial rinsing liquid for diswasher: a few drops are enough and quite well for getting large monolithic pieces of sold-gel glass. The drying must, however, be quite slow and may last for several weeks.
Alain
Dr Alain thank you very much for the suggestion. I would like to ask one more thing. If I use white vinegar as surfactant will that be Ok!
I don't believe that white vinegar will act as a good non-inoic surfactant, and moreover it will modify significantly the pH, with some consequences on the sol-gel reactions. A few drops of non-ionic surfactant is far better.
Alain
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