Role of carbon nanotubes on growth of a nanostructured double-deck tribofilm yielding excellent self-lubrication performance

Multi-walled carbon nanotubes (MWCNTs), and MWCNTs/zirconia nanoparticles (nano-ZrO2) hybrids were compounded into a formulated non-asbestos brake material of phenolic binder, respectively. It is demonstrated that even low-loading above nanofillers switching virtually the original brake material to an extremely wear-resistant self-lubricating material. More interestingly, the addition of MWCNTs/nano-ZrO2 hybrids leads to formation of a double-deck tribofilm yielding extraordinarily low friction and wear. First-principles calculations demonstrate that O atoms from air ambience break carbon-carbon backbones of CNTs, facilitating them to convert into graphitic nanograins. Our work provides direct evidence that graphitic nanograins and nano-ZrO2 are digested within the beneath layer of the tribofilm, whilst chelation of polymer chains radicals with nano-ZrO2 expedites formation of a carbon-based lubricous top layer. The present work puts forward a new strategy for endowing numerous mechanical motion systems with a robust self-lubrication characteristic via tuning tribofilms' nanostructures. (C) 2020 Elsevier Ltd. All rights reserved.