Layered double hydroxides for tribological application: Recent advances and future prospective

Ameliorating lubrication and reducing mechanical wear degree are of tremendous significance within the tendency of energy conservation. In the past decade, two-dimensional nanomaterials have flourished in the field of tribology. Among them, layered double hydroxide (LDH) features a unique crystalline structure, weak bonding, and easy adjustment of the interlayer spacing endowing its application potential in this field. It has been confirmed that LDH is equipped with prodigious properties to control tribological behavior and optimize the sliding conditions. So far, various LDH functional materials have been declared in wide applications ranging from liquid lubrication to solid lubrication. In this review, various controllable and feasible methods to improve anti-friction, anti-wear, and lubrication of pristine and modified LDH materials are presented. The specific tribological applications of LDH as oil-based additives, water-based additives, polymer fillers and coatings are systematically summarized. Additionally, the challenges and prospects of LDH in the field of lubrication are also discussed.