Size dependent thermal conductivity of single-walled carbon nanotubes J. Appl. Phys. 112, 013503 (2012) Inter-tube thermal conductance in carbon nanotubes arrays and bundles: Effects of contact area and pressure Appl. Phys. Lett. 100, 261908 (2012) The thermal flash technique: The inconsequential effect of contact resistance and the characterization of carbon nanotube clusters Rev. Sci. Instrum. 83, 054904 (2012) Thermal stability of wetting layer in quantum dot self-assembly J. Appl. Phys. 111, 093526 (2012) Additional information on Appl. Phys. Lett.

We have produced nanotube-in-oil suspensions and measured their effective thermal conductivity. The measured thermal conductivity is anomalously greater than theoretical predictions and is nonlinear with nanotube loadings. The anomalous phenomena show the fundamental limits of conventional heat conduction models for solid/liquid suspensions. We have suggested physical concepts for understanding the anomalous thermal behavior of nanotube suspensions. In comparison with other nanostructured materials dispersed in fluids, the nanotubes provide the highest thermal conductivity enhancement, opening the door to a wide range of nanotube applications.

2. Research Objectives Development and applications of nanoparticle analyzing techniques to examine their thermal behaviors in suspension, including the thermal conductivity, thermal (Brownian) diffusion, thermophoresis and thermocapillaryphoresis. 3. Itemized Progress 3-1. Development of a new miniaturized heated-wire conductivity measurement system Thermal conductivity measurements for CuO and Al 2 O 3 nanofluids have been performed with a newly-developed miniaturized heated-wire conductivity measurement device that require 10-ml capacity versus the first generation Argonne National Laboratory's system requiring 50-ml sample. The current data confirmed, within acceptable discrepancies, previously published data obtained by other research groups (Lee et al. 3 1999, Das et al. 4 2003) under identical conditions. Thus, the measurement accuracy of the newly developed miniaturized device has been validated. More detailed report is presented in Appendix 1. 3-2. Identification of surfactant effect on thermal conductivity When nanoparticles are mixed with base fluid, adding surfactant is essential to enhance the dispersion and minimize the coagulation of nanoparticles. Additionof surfactant, however, can unfavorably change the thermal characteristics of nanofluids. Using the developed miniaturized system, measurements have been made for thermal conductivities of nanofluids with surfactants. The results persistently show substantial decreases of the thermal conductivity in comparison with nanofluids with no surfactant mixed. In order to find the physical explanation for the reduced conductivity, both experimental and analytical studies are carefully explored to be implemented. More detailed report is presented in

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Effective thermal conductivity of mixtures of uids and nanometer-size particles is measured by a steady-state parallel-plate method. The tested uids contain two types of nanoparticles, Al 2 O 3 and CuO, dispersed in water, vacuum pump uid, engine oil, and ethylene glycol. Experimental results show that the thermal conductivities of nanoparticle-uid mixtures are higher than those of the base uids. Using theoretical models of effective thermal conductivity of a mixture, we have demonstrated that the predicted thermal conductivities of nanoparticle-uid mixtures are much lower than our measured data, indicating the de ciency in the existing models when used for nanoparticle-uid mixtures. Possible mechanisms contributing to enhancement of the thermal conductivity of the mixtures are discussed. A more comprehensive theory is needed to fully explain the behavior of nanoparticle-uid mixtures.Nomenclature c p = speci c heat k = thermal conductivity L = thickness Pe = Peclet number P q = input power to heater 1 r = radius of particle S = cross-sectional area T = temperature U = velocity of particles relative to that of base uids ® = ratio of thermal conductivity of particle to that of base liquid = .® ¡ 1/=.® ¡ 2/°= shear rate of ow ½ = density Á = volume fraction of particles in uids Subscripts e = effective property f = base uid property g = glass spacer p = particles r = rotational movement of particles t = translational movement of particles