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Thermal Conduction Coefficient in Single Wall Carbon Nanotubes. David R. Myers February 21, 2007 EE 235. Bulk Thermal Conductivity. Typical Values Air 26.3 X 10 -3 W/mK Glass 1.4 W/mK Gold 317 W/mK Graphite 1950 W/mK Diamond 2300 W/mK. T H. k. T C. T. x. Δ x. Microscopic Theory.
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Thermal Conduction Coefficient in Single Wall Carbon Nanotubes David R. Myers February 21, 2007 EE 235
Bulk Thermal Conductivity • Typical Values • Air 26.3 X 10-3 W/mK • Glass 1.4 W/mK • Gold 317 W/mK • Graphite 1950 W/mK • Diamond 2300 W/mK TH k TC T x Δx
Microscopic Theory • Thermal conductivity governed through free electrons interactions and phonons • Carbon nanotubes have very low scattering at the boundaries and thus high thermal conductivities Conserves Phonon Momentum Changes Phonon Momentum • Quantum of Thermal Conductance
Testing Apparatus Fabrication and Function • Heat one side • Measure the other resulting temperature • Use Q=(kA)(ΔT)
Measuring Thermal Conductivity • Nanowire Placement: • Sharp Probe to pick up sample • Nanowire Solution Spun on wafer • CVD to grow individual nanowires across gap • Cool Tricks for CVD: • Old - Spin solution onto wafer with catalyst nanoparticles • New – Sharp probe to directly deliver solutions onto membrane
Diamond Gold Results • Don’t really know the nanotube thickness, but makes a big difference • In any case, outperforms diamond • Umklapp Scattering is weak in 2.76 μm 1-3 nm CNT • Notice increasing temperature gives increasing conductivity (will continue until scattering dominates