Transmission and scanning electron microscopy images of test materials. A-B) Geometry and surface features of MWCNTs. SEM imaging (A) shows individual carbon nanotubes. MWCNT 1 shows encapsulated metal catalyst residues and MWCNT 3 shows amorphous surface carbon residues as imaged using HR-TEM (B). Both samples have the characteristic crystalline structure of carbon nanotubes. MWCNT geometry shows rigid tubes, iron catalyst residues embedded on the surface and encapsulated within well-ordered walls and surface with amorphous carbon debris. Analysis by TEM and HR-TEM. C) Crocidolite asbestos fibers are individually dispersed compared to cross-linking of MWCNTs into a 3D structure as shown by SEM imaging of native dry materials.