Although the mechanical behavior of carbon nanotubes has been studied extensively in recent years, very few experimental results exist on the shell buckling of nanotubes, despite its fundamental importance in nanotube mechanics and applications. Here we report an experimental technique in which individual multiwalled carbon nanotubes were axially compressed using a nanoindenter and the critical shell-buckling load was measured. The results are compared with predictions of existing continuum theories, which model multiwalled carbon nanotubes as a collection of single-walled shells, interacting through van der Waals forces. The theoretical models significantly underpredict the experimental buckling load.
We report experimental observations of shell buckling instabilities in freestanding, vertically aligned multiwalled carbon nanotubes subjected to uniaxial compression. Highly ordered and uniform arrays of carbon nanotubes embedded in an alumina matrix were fabricated and subjected to uniaxial compression using a nanoindenter. The buckling load was found to be on the order of 2μN for nanotubes with 25nm outer radius, 13nm inner radius, and heights of 50 and 100nm. Good agreement was found between the experimental observations and the predictions of linear elastic shell buckling theory.
We present an investigation into electromechanical coupling in carbon nanotubes by focusing on phonon frequency shifts as a result of charge injection. A nearest-neighbor, tight-binding theoretical model is accompanied by a computational explication carried out using the Vienna ab initio simulation package density functional theory code. Raman spectroscopic measurements of the electromechanic couplings under varied but controlled charge injection conditions are also carried out, and the close agreement between the model results and the measured Raman peak shifts suggests that geometrical changes of charged carbon nanotubes previously observed or speculated in different experiments can indeed originate from the simple quantum effects described herein.
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