Three dimensional (3D) percolation network structure: Key to form stablecarbon nano grease

Abstract

Nano grease is found to be stable and homogeneous (wherein carbon nanotubes act as sole thickeners and oil is polyalphaolefin (PAO)). This is a good indication that three dimensional (3D) percolation network structures among carbon nanotubes (single wall and multi wall) play a crucial role in stabilization. To better understand this assumption and provide further evidence, some additional carbon nanomaterials, such as carbon nanofiber (CNF), graphene, fullerene (C₆₀), Ni-coated single wall carbon nanotube (SWNT), are selected to make the grease. Unfortunately, CNF, graphene, fullerene (C₆₀) and Ni-coated SWNT do not form stable greases as nanotubes do. In addition, SWNTs were mixed with CNF and Ni-coated SWNT respectively to see if stable grease could be formed. The results indicate that the CNF/SWNT did not form the stable grease, while Ni-coated SWNT/SWNT did. Inter molecular Van der Waals forces could reasonably explain these experimental results. Appropriate tube size (nanotube and nanofiber), stereo structure (nanotube, graphene and fullerene), surface energy (nanotube and Ni-coated nanotube) are critical factors that determine if Van der Waals forces could take effect or not. The scientific merit of this paper is that we understand in what manner stable greases are formed and what kinds of carbon materials are appropriate for acting as sole thickener.