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

Abstract 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.