TC Study of Manufacturable Nano Grease: Evidence of 3D Network Structure

Surfactant-free grease made from carbon nanotube and carbon nanofibers has shown improvement in thermal conductivity. Time-dependent thermal conductivity (TC) magnetic study with different (Fe₂O₃ concentrations and Ni-coated carbon nanotubes) was performed. The results show that under the influence of a strong magnetic field, the TC value remains constant even with different processing times, magnetic fields, and Fe₂O₃ concentrations. An explanation for these results could be that for a high loading of CNTs (> 10 wt%), CNTs become associated strongly with each other by van der Waals forces and form a three-dimensional network (3D), which makes magnetic alignment of nanotubes very unlikely. A slight change on the TC of carbon nanofibers grease was noticed, which is probably because of the weak Van der Waals forces among the nanofibers. Mixing the CNFs with SWNTs produced a stable grease as SWNTs help to create the 3D network structure; however, the TC has dropped to 0.37 W/mK which is attributed to the lower TC of the SWNTs grease itself. The scientific merit of this paper is that the results provide further support that the CNTs form a 3D network structure and move forward the R&D work of manufacturable carbon nano grease.