Study of Radial Modulus of Single-walled Carbon Nanotubes by Atomic Force Microscopy Wenzhi Li, Florida International University, DMR 0548061.
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The understanding of the mechanical properties, especially the radial modulus (radial elasticity), of single-walled carbon nanotubes (SWCNT) is very important in developing SWCNT-based nanodevices. We have measured the radial modulus by combining tapping mode and contact mode atomic force microscopies on as-grown horizontally aligned SWCNTs.
It is found that the radius of the SWCNTs has a significant influence on the radial modulus. As shown in the right Figure, the measured radial modulus (Eradial) decreases from 57 to 9 Gpa as the radius of the SWCNTs increases from 0.92 to 1.91 nm.
We have analyzed our experimental data using Hertzian theory with the consideration of the deformation of the AFM tip-SWCNT-substrate system. The experimental data agrees well with the reported simulation result using a modified molecular structure mechanics (MSM) model.
Measured radial modulus (Eradial) vs. SWCNT radius (black squares ) compares with data from nanoindentation experiment (blue dots ) and modified MSM calculation data (red triangles, data courtesy of Mr. Y.L. Liu). Inset: The measured radial deformation (h) vs. applied normal force (Fz) as well as the fitting to the experimental data by using the power function relation Δh∝Fz2/3 for SWCNTs with radius from 1.91 to 0.42 nm.
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Undergraduate students have been provided the opportunity to gain research experience. The students work closely with postdoctoral associates, graduate students, and the PI to receive extensive research training. Six undergraduate students have been involved in the PI’s research in the last project year. Among the six undergraduate students, one is from Miami Dade College, one is from Auburn University, and the other four students are from FIU.
To expose many undergraduate students to nanomaterials research, the PI has offered an advanced curriculum titled “Widely Applied Physics” which combines classroom lectures, research presentations, lab tours, and research demonstrations.
Undergraduate student Melissa Chiarella is fabricating monolayer polystyrene nanosphere using self-assemble technique. She then uses the monolayer sphere as mask to deposit Ni catalyst nanoparticle array which will used for the growth of carbon nanotube array. She will continue to work in the lab in 2011-2012 to fulfill her “Advanced Research and Creativity in Honors program” supported by the Honors College at FIU.