Structural characterization and frictional properties of carbon nanotube/alumina composites prepared by precursor method

Multi-walled carbon nanotube (MWCNT)/Al2O3 composites with MWCNTs content up to 10 mass% were prepared by precursor method. XRD analysis revealed that MWCNT/Al2O3 composites were successfully synthesized by the dehydration of aluminum hydroxide–MWCNTs mixture at 1500 °C in vacuum. The steady-state friction coefficient (μ) of the composites decreased with increasing up to 4 mass% MWCNT and stayed constant (μ = 0.33) with further addition of MWCNT, which value was substantially lower than that of MWCNT-free monolithic Al2O3 (μ = 0.57). Microstructural observations showed that resultant friction behavior may be related to the smearing of transferred film over the contact area, which was expected to permit easy shear and then help to achieve a lubricating effect during sliding. However, fracture property tests have shown that no improvement of the fracture strength and fracture toughness of the composites was achieved by addition of MWCNTs. It may be mainly due to the agglomeration of MWCNTs and the weak interface between MWCNTs and the Al2O3 matrix.