Study on the Effect of Surface Modification on the Properties of Bentonite Greases

In order to investigate the influening factors of organic modification procedure and find out connections between organic modification and the properties of bentonite greases, organic montmorillonite(OMMT) thickeners with different surfactant dosages and constituents were synthesized through intercalation reaction between sodium montmorillonite(NaM MT) and quaternary ammonium surfactants in aqueous solvents. The lubricating greases were prepared with the resulting organoclays, while the penetration and oil separation of lubricating greases were evaluated, respectively. The surface modification process of montmorillonite(MMT) was analyzed and the thickening mechanism of OMMT was discussed in this study. The experimental results showed that, with an increasing amount of surfactant, the basal spacing between the clay platelets was increasing and the structure of modifier molecules layer in the interlayer was changing from lateral bilayer to paraffin-type bilayer. The optimal properties of lubricating greases were achieved, when the structure of surfactant molecules loaded in the interlayer was the paraffin-type monolayer, which meant that the dosage of modifier was equal to 120—140 mmol/(100g). Meanwhile, it was found that the thickening performance, colloid stability, anti-wear and friction-reducing performance of lubricating greases were improved, when the surfactants were mixed with octadecyl trimethyl ammonium chloride(OTAC) and hexadecyl trimethyl ammonium chloride(HTAC). And the optimum mole ratio of two surfactants is was 1:1.

Tribological properties of nanometer cerium oxide as additives in lithium grease

This paper presents a comparative study of the influence of nanometer-CeO_2（nano-CeO_2） and temperature on tribological and lubricating properties of lithium grease. The morphology and structure of nanocrystals were characterized by means of transmission electron microscopy（TEM） and X-ray diffraction（XRD）, respectively. Friction and wear tests were conducted on the friction and wear tester.Results show that the lithium grease with addition of nanometer-CeO_2 has much better friction-reducing and anti-wear performance than that of base grease. When the additive in grease is 0.6 wt%, the friction coefficient（COF） and wear scar diameter（WSD） decrease by 28% and 13% comparing with base grease,respectively. The base grease and grease with 0.6 wt% nanometer-CeO_2 both possess the lowest average COF and wear width at 50 ℃. The worn surface morphology after friction test was analyzed by scanning electron microscopy（SEM） and NANOVEA three-dimensional profilometer. Under the lubrication of the lithium grease containing 0.6 wt% nano-CeO_2. few shallow furrows can be observed on the quite smoothed surface and the WSD decreased. Moreover, It was found that the nano-CeO_2 has been incorporated into the surface protective and lubricious layer by energy dispersive spectrometer（EDS） analysis.