Stability and thermal conductivity of water-based carbon nanotube nanofluids--颗粒学报PARTICUOLOGY

Farbod, M., Ahangarpour, A., & Etemad, S. G. (2015). Stability and thermal conductivity of water-based carbon nanotube nanofluids. Particuology, 22, 59-65. https://doi.org/10.1016/j.partic.2014.07.005

Stability and thermal conductivity of water-based carbon nanotube nanofluids

Mansoor Farbod ^a *, Ameneh Ahangarpour ^a, Seyed Gholamreza Etemad ^b

a Department of Physics, Shahid-Chamran University, Ahvaz, Iran
b Department of Chemical Engineering, Isfahan University of Technology, Iran

10.1016/j.partic.2014.07.005

Volume 22, October 2015, Pages 59-65

Received 3 June 2014, Revised 29 June 2014, Accepted 9 July 2014, Available online 18 November 2014, Version of Record 4 August 2015.

E-mail: farbod_m@scu.ac.ir

Highlights

• CNTs were functionalized via refluxing to lessen their lengths and improve dispersion stability.

• The nanofluids prepared using functionalized CNTs can keep stable for more than 80 days.

• Thermal conductivity of nanofluids prepared using refluxed CNTs was higher than unrefluxed ones.

• Thermal conductivity of the prepared nanofluids increased with increasing the temperature.

Abstract

Water-based nanofluids were prepared with multi walled carbon nanotubes (MWCNTs) of different lengths in concentrations of 0.1, 0.25 and 0.5 vol%. To improve their dispersibility, pristine MWCNTs were functionalized and cut into small lengths by reflux in an oxidizing mixture of 3:1 sulfuric and nitric acids. The initial length of the carbon nanotubes (CNTs; 10–15 μm) was reduced to 203, 171 and 134 nm after 1, 2 and 4 h of reflux, respectively. Surface modification and the reduced length of the CNTs, improved the stability of the nanofluids with no significant sedimentation observed after 80 days. Furthermore, the thermal conductivities of nanofluids prepared using refluxed CNTs, were higher than that of the pristine CNTs. The thermal conductivity also increased with the nanofluid temperature. The nanofluid prepared with 1 h refluxed CNTs had the highest thermal conductivity. The enhanced thermal conductivity and stability of the nanofluids was attributed to the decreased length of CNTs.

Graphical abstract

Keywords

Nanofluids; Thermal conductivity; Stability; Carbon nanotubes; Refluxing time

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