Nano-Engineered Structural Joints with Improved Thermal Properties

Introduction of nanomateials within joints can provide for improved heat transport qualities, thermal stability, conformability and structural performance.

1. Nano-Engineered Joints with High Strength and Heat Conduction Parviz Soroushian

2. Nano-Engineered Joints Conformable joints with desirable large-cycle fatigue life Effective heat transport Adequate structural performance High-temperature stability

3. Merits: Unique Qualities of Nanomaterials Examples: carbon or boron nitride nanotubes; copper or tungsten nanowires Multiwalled carbon nanotubes: Measured thermal conductivity ~2000 W/mK ~50 GPa tensile strength, ~1,000 GPa elastic modulus Large elastic strains; High-temperature stability/ductility Extreme/reversible bending capability Yan, X. H., Y. Xiao, et al. (2006). "Effects of intertube coupling and tube chirality on thermal transport of carbon nanotubes." Journal of Applied Physics 99(12): 124305. Huang, J. Y., S. Chen, et al. (2007). "Enhanced ductile behavior of tensile-elongated individual double-walled and triple-walled carbon nanotubes at high temperatures." Physical Review Letters 98 (18): 185501. Bernholc, J., D. Brenner, et al. (2002). "Mechanical and electrical properties of nanotubes." Annual Review of Materials Science 32: 347-375.

4. Merits: contd. Other nanomaterials The thermal & mechanical attributes of boron nitride and other nanotubes approach those of carbon nanotubes. Metal nanowires provide mechanical properties far superior to those of bulk metals . Chang, C. W., A. M. Fennimore, et al. (2006). "Isotope effect on the thermal conductivity of boron nitride nanotubes." Physical Review Letters 97 (8): 085901. Wu, B., A. Heidelberg, et al. (2005). "Mechanical properties of ultrahigh-strength gold nanowires." Nature Materials 4(7): 525-529. Liang, W. and M. Zhou (2005). "Pseudoelasticity of single crystalline Cu nanowires through reversible lattice reorientations." Journal of Engineering Materials and Technology, Transactions of the ASME 127 (4): 423-433.

5. Challenges & Considerations Nanotube/metal contact thermal resistance Intertube contact resistance in mats (~50 W/mK mat conductivity vs. ~2000 W/mK nanotube conductivity Anisotropic thermal transport in aligned arrays (anisotropy ratio of ~70) Nanotube/metal and intertube contact mechanical resistance Size effects on melt behavior and thermal conductivity Xu, J. and T. S. Fisher (2006). "Enhanced thermal contact conductance using carbon nanotube array interfaces." IEEE Transactions on Components and Packaging Technologies 29(2): 261-267. Ivanov, I., A. Puretzky, et al. (2006). "Fast and highly anisotropic thermal transport through vertically aligned carbon nanotube arrays." Applied Physics Letters 89(22): 223110. Yan, X. H., Y. Xiao, et al. (2006). "Effects of intertube coupling and tube chirality on thermal transport of carbon nanotubes." Journal of Applied Physics 99(12): 124305.

6. Addressing the challenges Nanomaterial/metal contact Embedment in molten metal Diffusion bonding of metal nanowire or metal-coated nanotube Direct growth of nanomaterial on metal Intertube contact Merging/welding Chemical bonding