Fabrication of Vanadium Oxide-encapsulated Hybrid Carbon Nanospheres for Enhanced Tribological Performance.

A new sulfur-containing carbon nanospheres encapsulated with vanadium oxide (V@SCN) is synthesized through a one-pot oxidation polymerization and then carbonization method. The prepared V@SCNs exhibit good dispersibility as a lubricant additive, which is owing to the inherited lipophilic organic functional groups in the sulfur-containing carbon shell derived from the carbonization of polythiophene. The agglomeration and precipitation of metals in the base oil are also avoided through the encapsulation of lipophilic carbon shells. The stress and thermal simulation results show that the vanadium oxide core bestows upon the carbon nanospheres enhanced load resistance and superior thermal conductivity, which contributes to their excellent tribological properties. Introducing 0.04M-V@SCN to the base oil leads to favorable tribological characteristics, such as a fourfold rise in extreme pressure capacity from 250 to 1050N, a reduction in friction coefficient from 0.2 to ≈0.1, and a substantial decrease in wear by 90.2%. The lubrication mechanism of V@SCNs as lubricant additive involves the formation of a robust protective film on the friction pair, which is formed via complex physical and chemical reactions with the friction pair during friction.