Internal and external MoS2/GO heterostructure enhanced multi-point contact egg-box inspired SiOC for macroscopic ultra-low friction

Superlubricity, as a tribological state in which friction and wear virtually disappear, has aroused strong scientific interest. However, scaling superlubricity from nano/micro-scale to macroscale still remains a challenge, owing to the increase in surface defects and elastic deformation under large contact areas. Herein, inspired by egg-box foams, 3D-printed SiOC–MoS2/GO structural lubricating composites were developed by introducing MoS2/GO heterostructure into the interior and surface of well-designed SiOC structures. The 3D highly rigid egg-box like SiOC structures enable an ingenious transformation from macroscopic planar contact to microscopic point contact and a powerful reduction of surface elastic deformation, while 2D MoS2/GO heterostructure ensures the establishment of sustainable incommensurability, thereby improving the macroscopic lubrication performance. As expected, the egg-box like structure with a curvature of 1.57 achieves a minimum wear depth of 1.22 × 10−7 mm. Meanwhile, the corresponding structural composites containing MoS2/GO both inside and outside realize a stable ultra-low friction coefficient of 0.09 in 18,000 reciprocating cycles under dry sliding conditions. The high hardness, multi-point contact, and continuous incommensurable interfaces are responsible for such extraordinary lubricity, according to the finite element calculation and experimental analyses. Admittedly, this work opens up a promising avenue for accelerating the application of superlubricity in future industrial systems.