Stable low‐friction carbon/epoxy composites using carbon nanocages stuffed with ionic liquids as fillers

Epoxy resin (EP) is prone to brittle fracture during friction due to internal stress after curing, resulting in fatigue wear and cracking. Adding carbon fillers is considered as one of the great potential solutions to solve the serious dry wear of EP. Herein, we develop a novel carbon capsule composite filler (CNC‐IL) filled with ionic liquid (IL) in carbon nanocages (CNC) using the vacuum principle to address these concerns. Compared with pure EP, the friction coefficient (0.10) and wear rate (1.712 × 10−6 mm3 Nm−1) of the optimized CNC‐IL/EP were reduced by 74.62% and 88.14%, respectively. Such excellent tribological properties can be attributed to the solid–liquid lubricating film formed by the IL released from the broken CNC during friction. A low‐shear‐resistance slip layer can be formed between the CNC‐IL in the film due to the repulsion of the isoelectric ions adsorbed on the surface of the CNC; it effectively integrates the self‐lubricating functions of CNC and the liquid lubrication functions of ILs. This work provides a valuable idea for designing C/EP composites with good antifriction properties.