Little amounts of carbon nanotubes as anti-wear reinforcement for alumina in dry sliding

Carbon nanotubes (CNTs) are a leading choice for reinforcing oxide and nitride ceramics, but investigations into the tribological performance of CNT-ceramic composites remain inconclusive. Here, we show that reinforcement with only .1 wt% multi-walled CNTs improves the antifriction and anti-wear performance of zirconia-toughened alumina by up to 23% and 51%, respectively. Dry sliding tests under normal loads of 40-60 N for a sliding distance of 1000 m reveal a load-dependent transition in the lubrication mechanism-CNTs retain their tubular morphology at low loads and reduce friction via a sliding-rolling response, whereas high sliding loads trigger the formation of a uniform, thin lubricating film by the repeated crushing and smearing of exfoliated nanotubes. Raman spectra analyses confirmed that the carbon-rich tribo-film possesses a graphitic structure. Well-dispersed CNTs prevent wear loss by mechanisms, such as crack bridging and grain anchoring. The present work opens up new frontiers for the application of CNT-alumina tribo-ceramics in anti-wear, unlubricated, and high contact stress applications, such as in the manufacturing and mining industries.

Automated summary

Research shows that the addition of 0.1 wt% multi-walled carbon nanotubes (MWNTs) significantly improves the antifriction and anti-wear performance of zirconia-toughened alumina. Dry sliding tests reveal a load-dependent transition in the lubrication mechanism, where low loads result in reduced friction through sliding-rolling response of CNTs, and high loads lead to the formation of a uniform lubricating film through the crushing and smearing of nanotubes. This work opens new possibilities for the application of CNT-alumina tribo-ceramics in industries such as manufacturing and mining.