Explosive shock-wave consolidation of aluminum powder/carbon nanotube aggregate mixtures: Optical and electron metallography
The formation of conventional metal-matrix composites from carbon nanotubes has proven to be difficult because of their agglomeration and inability to disperse. We have explored the explosive consolidation of 150 µm aluminum powder/multiwalled carbon nanotube (MWCNT) aggregates (including multiconcentric fullerenes) at volume percentages of 2 and 5%. These consolidated mixtures formed 2-phase, monolithic systems with the MWCNT aggregate material spreading along the Al grains and forming carbon phases at the Al particle triple points. The Al powder particle (or grain) hardness increased from HRE 22 to HRE 40 for the consolidated Al while the 2-phase system hardness dropped from HRE 40 to HRE 39 and 33 respectively for 2 and 5% (volume) MWCNT aggregate additions. TEM and SEM observations illustrate a laminate-like structure of the consolidated MWCNT aggregate material, which is easily delaminated, causing intergranular (Al) failure. The Al grains exhibited a shock-induced dislocation substructure (0.5-3 µm) and recrystallized sub-grains, which increased the individual particle/grain Vickers hardness from HV 24 to HV 43.
Salas, Wayne, "Explosive shock-wave consolidation of aluminum powder/carbon nanotube aggregate mixtures: Optical and electron metallography" (2006). ETD Collection for University of Texas, El Paso. AAI1439485.