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Abstract: In this study, soft sphere surfactants, with varying head group charges and alkyl chain lengths, were investigated for their effects on the thermal conductivity, rheology, density, contact angle and refractive index of nanofluids. Using the Hot Disk TPS 2500S, it was noted that the thermal conductivity of the ionic surfactant micelles follows the effective medium theory of poor thermal conductance, with interfacial resistance towards infinity. It was also determined that the longer the alkyl chains on the nonionic surfactant micelles, the lower the thermal conductance at lower concentration and higher interface tensions. The adsorbed moieties were found to enhance the stability of the nanoparticles in the base fluid. The orientation of the cylinders and their aspect ratios are key to the thermal conductivity enhancement within the nanofluids, as cylinders with a high aspect ratio and an organized orientation, have an enhanced thermal conductivity. With the results observed, it was determined that these nanofluids may be useful for thermal management.

Reference: Journal of Physical Chemistry C, 117:17 (2013) 9009–9019

DOI: 10.1021/jp401792b