Controlled Synthesis of Mg Al-Layered Double Hydroxide as a High-Performance Additive of Bentonite Grease

Traditional bentonite grease suffers from inadequate tribological properties. Layered double hydroxides (LDHs) have great potential as lubricant additives owing to their unique lamellar structure, tunable chemical composition, and high anion-exchange capacity, which enable strong interfacial interactions and stable dispersion in lubricating media. In this study, Mg Al-layered double hydroxide (MA-LDH) was synthesized as a crystalline lamellar compound with a controllable morphology and particle size. MA-LDH was prepared under hydrothermal conditions at pH 8-12 and 120-180 °C. The effects of MA-LDH synthesis conditions and additive concentration on the properties of bentonite grease were systematically investigated. Scanning electron microscopy revealed that the particle size distribution of MA-LDH became increasingly nonuniform as the pH and hydrothermal temperature increased. MA-LDH synthesized at pH 10 and 120 °C exhibited excellent particle size uniformity and dispersibility. Within the investigated additive range (0.1-12 wt %), an MA-LDH concentration of 1.5 wt % produced the best tribological performance. Compared with the base bentonite grease, the grease containing 1.5 wt % MA-LDH showed a 34.2% reduction in average coefficient of friction, an 89.2% decrease in wear volume, and a 150% increase in load-carrying capacity. The incorporation of MA-LDH optimizes load distribution, facilitates interfacial sliding, and enhances the film-forming ability, thereby improving the tribological performance of the bentonite grease.