The silica nanoparticles may be in powder form. If they are distributed in a liquid, then it is a suspension. If in suspension they are not visible to the human eye, then this is a colloidal dispersed system. If visible to the human eye (larger than nano), then it is just a suspension or a coarse suspension. These are three different thermodynamic systems that differ in different components or phases. The powder contains only the solid phase. In a colloidal suspension, there are 2 phases of nanosilica and water. In a suspension of 2 phases, silica with coarse particles and water.
Nano silica powder is a dry, free-flowing form of nano silica particles, while colloidal nano silica is a stable suspension of nano silica particles in a liquid medium. Nano silica slurry is a concentrated form of nano silica suspension with a higher solid content.
Colloidal nano-silica has better dispersibility of nano-silica particles compared with powdered nano-silica as well as due to the high specific surface area for colloidal nano silica (CNS) particles they contribute a highly reactive siliceous material.
Reference:
Kim T, Kim JH, Jun Y. Properties of Alkali-Activated Slag Paste Using New Colloidal Nano-Silica Mixing Method. Materials (Basel). 2019;12(9):1571. Published 2019 May 13. doi:10.3390/ma12091571