Cellulose-armored “CNTs-soft metal” hybrid nanomaterials to improving the friction-reduction and anti-wear performance of bio-lubricants

Surface-inert carbon nanotubes (CNTs) exhibit poor interfacial compatibility with bio-oils and are prone to aggregation and precipitation which hinders their lubricity and anti-wear properties. Herein, polydopamine (PDA) was introduced to the surface of CNTs (CNTs-PDA) and constructed nanocellulose "armor" on the CNTs-PDA surface through hydrogen bonding effect (from amino and hydroxyl groups) to enhance the interfacial compatibility of carbon nanotubes with vegetable oils. The cellulose-armored "CNTs-soft metal" hybrid nanomaterial was used as a lubricant additive in sunflower oil, reducing the friction coefficient and wear rate of engineered steel surfaces by 61.9% and 79.5%, respectively. Furthermore, the tribo-chemical changes and lubrication mechanisms occurring at wear scars were revealed by the wear analysis, Raman spectrum, and lubrication theory calculations.