Dear Sahar Qavi,

you can use cryogenic microtoming, i.e:; to freeze your sample until it becomes a solid and after that cut thin slides:

Other option sometimes used is to find conditions for thin film deposition of the aerogel. Regards

U can dip the sample in water overnight. As it soaks in water... it will rise to the top. 

P.S. Only if it is not water soluble. U can dry it overnight then before observing under SEM.

Hello Sahar Qavi,

If your sample is not affected by ethanol, you could try a so called "poor-man cryo" procedure:

1. Soak your sample in absolute (100%) ethanol

2. Put the sample into liquid nitrogen and wait for some time

3. Break your sample into pieces under liquid nitrogen

4. Transfer the pieces back into absolute ethanol

5. Dry your samples in the critical-point dryer

Regards

Oldrich