Wood-powder-template-based syntheses and tribology of copper oxide particles as lubricating oil additives

Abstract

Copper based particles were synthesized by a wood-powder-template-based process. Wood powders mixed with an aqueous cooper salt solution were heated under N2 gas flow, and then, the mixture of the charcoal powder and copper particles were heated in air to remove charcoal. Finally, oxidized wood-derived copper particles (OWCu) of less than 1 μm were synthesized. Wood powders acted as the template and limited the sizes of the copper particles. In addition, the tribological properties of OWCu in synthetic oil were investigated using a pin-on-plate reciprocating tribometer. Our results revealed that 0.5 mass% OWCu reduced both the friction coefficient (max 45%) and wear volume (max 39%) of SUJ2 lubricated by PAO4. The best reduction effect was obtained for OWCu synthesized at 400°C under N2 gas flow, which had the smallest average particle size, where the coverage of the OWCu layer on the wear track was the largest. These facts suggest that the particle size reduction of OWCu can increase the coverage and improve the friction coefficient and wear volume reduction effects of the lubricant. Control of the wood-powder-template-based synthesized particles to the optimal size for the roughness of the sliding surface would help achieve better tribological performance.