You can create thermite in the lab using aluminum and rust oxide and igniting them under high temps.
the operative word is unreacted nanothermite.
what you suggest has been ruled out. the nanothermite has been analysed and found to contain iron oxide and elemental aluminium organised uniformly at the nanoscale which means it is engineered to be that way. sorry, but under entropy laws it is an absurdity to suggest that chaotic collisions produces unreacted nanothermite.
"You left out the significant presence of organic material found in the red chips – where did that come from? Not so easy. You also need to explain how the aluminum can end up on 40-nanometer thin platelets as observed in our electron-microscope studies of the material from the WTC dust. Get serious. The observed mix has nano-components which do not organize themselves into a highly active form (including organics) from larger objects in violation of the laws of physics"
- Niels Harrit