Pushing the boundaries of the thermal conductivity of materials

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Conclusions from theoretical work (Hu and Keblinski, unpublished) • Analysis of the participation ratio: phonon localization is not significant. • Analysis of mode polarization: incoherent grain boundaries create diffusive but non-propagating vibrational modes. (stacking faults are not sufficient) • Key to ultralow thermal conductivity is disorder in combination with anisotropy, i.e., an “anisotropic glass”. • Interface resistance between 2D crystalline sheets? Lowering of the effective density of states for modes diffusing perpendicular to the sheets?
Back to experiment: Can we lower the conductivity even further? • Synthesize misfit layered compounds by elemental reactants method (Johnson and co-workers) –WSe2 /PbTe –MoSe2 /PbTe • Interface density does not matter. Conductivity determined by composition not interface density. Λ (W m -1 K -1 ) 0.3 0.1 (2;3) (1;3) (1;5) (1;2) (2;1) (2;2) (3;3) (1;1) (4.5;1) (3;1) (PbSe) m : (MoSe2 ) n 0.03 0.0 0.2 0.4 0.6 0.8 1.0 PbSe content
Page 1 and 2: Pushing the boundaries of the therm
Page 3 and 4: Interfaces are critical at the nano
Page 5 and 6: Thermal conductivity and interface
Page 7 and 8: Brief introduction to thermoelectri
Page 9 and 10: Carbon nanotubes • Evidence for t
Page 11 and 12: Critical aspect ratio of a fiber co
Page 13 and 14: psec acoustics and time-domain ther
Page 15 and 16: Windows software author: Catalin Ch
Page 17 and 18: Thermal conductivity map of a human
Page 19 and 20: Critical aspect ratio of a fiber co
Page 21 and 22: Can we beat the amorphous limit of
Page 23 and 24: Works well for homogeneous disorder
Page 25 and 26: W/Al 2 O 3 nanolaminates • ultra-
Page 27 and 28: Cross-sectional TEM of 60 nm thick
Page 29 and 30: Ion irradiation of WSe 2 MD simulat
Page 31: Molecular dynamics simulation • M
Page 35: Conclusions • Difficult to take a

Pushing the boundaries of the thermal conductivity of materials

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