Dear Atia Sandhu, please check the following link. My Regards

https://www.hielscher.com/power-ultrasound-for-particle-treatment-application-notes.htm

SEM measurement gives you structural information about nanoparticles. So, your objective is to break down larger agglomerated particles into smaller ones to see the structure that is repeating all-time in your sample. For this, peoples use sonication to get structures of micron particles in solvent like water and ethanol. In the case of CaCo3 nanoparticle as it is not soluble in water and ethanol you need acid to dissolve it as mentioned by Abdelkader BOUAZIZ sir. But the addition of acid to dissolves CaCO3 will produce carbon dioxide. So your CaCO3 nanoparticle structure also might get affected. Better you should directly measure SEM of your powder sample (powder SEM) without any solvents.

Dear Atia Sandhu ,

I recommend this paper it will help you for your inquiries.

Article Dispersion of CaCO3 nanoparticles by sonication and surfacta...