Lithium-Calcium Greases Having Carbon Nanotubes and Aluminum Oxide Base Nanoadditives: Preparation and Characteristics of Nanogrease.

This research presents the results of the effect of different concentrations (2, 4, 6, and 8 wt %) of multiwall carbon nanotubes (MWCNTs) and aluminum oxide nanoparticles (AlO) on the characteristics of lithium-calcium grease (LCG). The LCG/AlO and LCG/MWCNT were studied and illustrated by measuring the dropping point, consistency, thermal conductivity, and tribological characteristics of nanograins (wear, friction, and welding point) by using a four-ball tribometer. The morphologies of the additives and the nanogrease were examined and evaluated by X-ray diffraction and transmission electron microscopy. The worn surface of the ball surface was assessed by scanning electron microscopy. Based on the obtained results, the nanoadditive can significantly enhance the grease properties. The grease having a 4 wt % content of AlO and MWCNT presented the lowest wear scar diameter and friction coefficient. Consequently, the welding point, dropping point, and thermal conductivity indicated that adding nanoadditives could strikingly enhance the lubricating effect of grease by 26, 32, and 75%, respectively. Finally, this study provides a lubricant with promising results that can be used under extreme pressure.