Graphene as a nanofiller for enhancing the tribological properties and thermal conductivity of base grease

Artificial Intelligence-Based Rapid Design of Grease with Chemically Functionalized Graphene and Carbon Nanotubes as Lubrication Additives

Rapid chemical functionalization of additives and efficient determination of their optimum concentrations are important for designing high-performance lubricants, especially under multi-additive conditions. Herein, chemically functionalized graphene (FGR) and carbon nanotubes (FCNTs) were rapidly prepared by microwave-assisted ball milling and subsequently introduced into grease as additives. The tribological properties of the additives in grease at different concentrations and ratios were measured using a four-ball test. A reliable artificial neural network (ANN) model was established according to a few test results. Subsequently, the optimal concentration of multiple additives in the grease was predicted using a genetic algorithm and experimentally validated. The results indicated that the introduction of FGR (0.14 wt %) and FCNT (0.16 wt %) improved the antifriction and anti-wear performance of the base grease by 25.66 and 29.34%, respectively. The results of the ANN model analysis and friction interface characterization indicate that such performance is principally attributed to the synergistic lubrication of the FGR and FCNT.

Flake Graphene as an Innovative Additive to Grease with Improved Tribological Properties

The paper presents the results of research on the use of flake graphene as an additive to plastic grease in order to improve its tribological properties. The influence of concentration (0.25-5.00 wt.%) and the form of graphene (graphene oxide, reduced graphene oxide) on selected properties of the base grease were investigated. It has been found that the addition of graphene flakes improves the anti-wear properties of the lubricant. The greatest improvement in the properties of the lubricant was achieved by using graphene at a concentration of 4.00 wt.%; the reduction in the average diameter of the wear scar was almost 70% for GO and RGO, compared to the base lubricant without the addition of graphene.

Impact of Graphene Nano-Additives to Lithium Grease on the Dynamic and Tribological Behavior of Rolling Bearings

In recent years, reduced graphene oxide (rGO) received considerable interest as a lubricant nano-additive for enhancing sliding and rolling contacts. This paper investigates the tribological and dynamic behavior of ball bearings lubricated by lithium grease at different weight percentages of rGO. Full bearing tests were conducted for experimental modal analysis, vibration analysis, ultrasonic analysis, and infrared thermography. Modal analysis indicated considerable improvements of the damping ratio values up to 50% for the bearings with rGO nano-additives. These findings were confirmed by the corresponding reductions in vibrations and ultrasound levels. The steady-state temperatures of bearings running with lithium grease reached 64 °C, whereas the temperature of bearings lubricated by grease with 2 wt.% rGO measured only 27 °C. A Timken Load test was conducted on grease samples with and without rGO additives. Grease samples having 2, 3.5, and 5 wt.% rGO showed the highest OK load with an increase of 25%, 50%, and 100% as compared to values of lithium grease. For comparison, all tests were conducted on samples of the same grease blended with graphite and MWCNTs’ nano-additives. The results proved the superiority of graphene in enhancing the load-carrying capacity and damping of grease in rolling bearings.