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Electrically Insulating Thermal Nano-Oils Using 2D Fillers

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Jaime Taha-Tijerina†‡, Tharangattu N. Narayanan†, Guanhui Gao†§, Matthew Rohde†, Dmitri A. Tsentalovich

, Matteo Pasquali

, and Pulickel M. Ajayan†

^† Department of Mechanical Engineering and Materials Science, Rice University, Houston, Texas 77005, United States

^‡ Prolec GE Internacional, S. de R.L. de C.V., Monterrey, NL, México

^§ College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao, China

Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, United States

ACS Nano, Article ASAP

DOI: 10.1021/nn203862p

Publication Date (Web): January 24, 2012

*Address correspondence to ajayan@rice.edu.

Author Contributions

These authors contributed equally to this work.

Abstract

Different nanoscale fillers have been used to create composite fluids for applications such as thermal management. The ever increasing thermal loads in applications now require advanced operational fluids, for example, high thermal conductivity dielectric oils in transformers. These oils require excellent filler dispersion, high thermal conduction, but also electrical insulation. Such thermal oils that conform to this thermal/electrical requirement, and yet remain in highly suspended stable state, have not yet been synthesized. We report here the synthesis and characterization of stable high thermal conductivity Newtonian nanofluids using exfoliated layers of hexagonal boron nitride in oil without compromising its electrically insulating property. Two-dimensional nanosheets of hexagonal boron nitride are liquid exfoliated in isopropyl alcohol and redispersed in mineral oil, used as standard transformer oil, forming stable nanosuspensions with high shelf life. A high electrical resistivity, even higher than that of the base oil, is maintained for the nano-oil containing small weight fraction of the filler (0.01 wt %), whereas the thermal conductivity was enhanced. The low dissipation factor and high pour point for this nano-oil suggests several applications in thermal management.