In situ SEM Observation of Column-like and Foam-like CNT Array Nanoindentation

Quantitative nanoindentation of nominally 7.5 and 600 mu m tall vertically aligned carbon nanotube (VACNT) arrays is observed in situ within an SEM chamber. The 7.5 mu m array consists of highly aligned and weakly interacting CNTs and deflects similarly to classically defined cylindrical columns, with deformation geometry and critical buckling force well estimated using the Euler-Bernoulli theory. The 600 mu m array has a highly entangled foam-like morphology and exhibits sequential buckle formation upon loading, with a buckle first forming near the array bottom at approximately 2% strain, followed by accumulating coordinated buckling at the top surface at strains exceeding 5%.