Thermal Anisotropy In Carbon Nanotubes Measured by Transient Thermotransmittance and Anisotropic Effects on Reaction Rates In Composites

Joel T. Abrahamson1, Nitish Nair1, and Michael S. Strano2. (1) Department of Chemical Engineering, Massachusetts Institute of Technology, Building 66-153, 25 Ames St, Cambridge, MA 02139, (2) 66-566 Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139

Transient thermotransmittance (TTT) offers a way to measure thermal conductivity and interfacial resistance in nanomaterials. TTT measurements on aligned arrays of carbon nanotubes help us to study their anisotropic heat transport properties. We can also examine the effects of covalent functionalization. Nor is TTT limited to materials made only of nanotubes. An attractive target for study is a novel nanocomposite where single-walled carbon nanotubes (SWNT) are surrounded by highly energetic metal nanoparticles or organic molecules. Our simulations of the energy balances for a SWNT coated with reactive Zr metal and oxide indicate that coupling to thermal transport in the nanotube accelerates reaction front velocity along the length of the Zr annulus from 530 to 5100 mm/s. This offers a proof-of-concept for one-dimensional anisotropic energetic materials, which could find new applications in inorganic synthesis and novel propellants. Nanotube conductivity and the relative sizes of the annulus and the nanotube limit the reaction velocity enhancement, rather than interfacial resistance. This is due to the large temperature differences between nanotube and annulus at the reaction front.

[1] J. T. Abrahamson, N. Nair, M. S. Strano. Nanotechnology. 19, (2008), 195701

[2] P. M. Norris et al. Rev. Sci. Instr. 74, (2003), 400