Scholar: Cordero Nuanez
Major: Chemical Engineering
Faculty Mentors: Dr. Siddhartha Pathak
Research Topic: In-situ SEM micro-compression behavior of vertically aligned carbon nanotube (VACNT) brushes
Abstract: Layers of vertically aligned carbon nanotubes (VACNTs), known as VACNT brushes, have been suggested for applications in superhydrophobic, compliant and energy-absorbing coatings. While the individual carbon nanotubes (CNTs) have been announced as the strongest material known, much less is known about VACNTs in terms of their mechanical behavior under compression. In this work, we study the mechanical response of arrays of highly dense brushes of small-diameter (1-3 nm) non-catalytic multiwall (2-4 walls) VACNT brushes, measured using scanning electron microscopy (SEM) in-situ micro-pillar compression testing.
These highly dense VACNT brushes were produced by high temperature vacuum decomposition of 6H SiC single crystals using the carbide-derived carbon (CDC) technique. In this technique, the conformal transformation of SiC into carbon results in a very high density (~0.95 g/cm3), which is 10 or more times higher than VACNTs produced by other techniques, and a very small 0.35 nm inter-tube distance. At this small inter-tube distance, electron beam irradiation has been shown to introduce stable links between neighboring carbon nanotube. The purpose of this current work is to study the mechanical behavior of VACNTs subjected to such inter-tube bridging.
We utilize focus ion beam (FIB) micromachining technique to fabricate VACNT micro-pillars of varying diameters with varying degrees of intertube bridging. Our results show that increasing the volume of the crosslinked region in VACNT pillars results in an increase of their mechanical properties under compression such as their elastic moduli (which increases from ~13 GPa to ~100 GPa) and yield strength (from ~ 0.5 GPa to 4 GPa), but decreases the viscoelastic response (as well as ability to withstand large strains) of the VACNTs. These results are explained in terms of VACNT inter-tube bridging, and the lack of sliding between CNTs in their crosslinked state.
New Scholar: 2016 cohort
Graduating with a Baccalaureate Degree: 2017