Highly thermo-conductive fluid with boron nitride nanofillers.

We report for the first time how boron nitride (BN) nanotubes and nanospheres may effectively be used to achieve remarkable thermal conductivity improvement of a fluid. Benefiting from high thermal conductivity and high-aspect-ratio of BN nanotubes, at a fraction of 6 vol %, the thermal conductivity of water was remarkably improved, up to ∼2.6-times. With BN nanospheres as fillers, the viscosity of the fluid can be kept decently low and thermal conductivity can also be effectively improved. A combination of BN nanotubes and nanospheres was found to increase the fluid's thermal conductivity while keeping its viscosity low, thus, such mixtures can be promising fillers for highly thermo-conductive fluids. Finally, calculations based on finite element method were used to investigate the regarded nanofluids. On the basis of the results, thermal conductivity was estimated to be more than, or close to 200 W/mK for BN nanotubes and nanospheres, respectively.