Ni-P-carbon nanotube (CNT) composite coating and carbon nanotube/copper matrix composites were prepared by electroless plating and powder metallurgy techniques, respectively. The effects of CNTs on the tribological properties of these composites were evaluated. The results demonstrated that the Ni-P-CNT electroless composite coating exhibited higher wear resistance and lower friction coefficient than Ni-P-SiC and Ni-P-graphite composite coatings. After annealing at 673 K for 2 h, the wear resistance of the Ni-P-CNT composite coating was improved. Carbon nanotube/copper matrix composites revealed a lower wear rate and friction coefficient compared with pure copper, and their wear rates and friction coefficients showed a decreasing trend with increasing volume fraction of CNTs within the range from 0 to 12 vol.% due to the effects of the reinforcement and reduced friction of CNTs. The favorable effects of CNTs on the tribological properties are attributed to improved mechanical properties and unique topological struct ure of the hollow nanotubes.

Amorphous carbon nanofiber arrays were synthesized in porous anodic aluminum oxide templates by pyrolysis of acetylene with cobalt nanoparticles as catalyst at 640 8C. The carbon nanofibers have amorphous structures under high-resolution transmission electron microscopy and Raman spectroscopy examination. The aligned amorphous carbon nanofibers grown within the pores of the aluminum oxide membranes are uniform with lengths of about 2μm and outer diameters of about 85 nm. The frictional properties of the array film of amorphous carbon nanofibers were investigated using an atomic force and friction force microscopy (AFM-FFM) and a ball-on-disk machine in air. The adhesion between the amorphous carbon nanofiber arrays and the anodic aluminum oxide membrane remained intact at relatively low loads. The AFM-FFM measurements indicated that the friction forces on the array film of amorphous carbon nanofibers were uniform. The array film had low friction coefficient and high wear resistance under the micro friction tests. The friction coefficient of the array film dry sliding against a corundum counterface was observed to be constant after an initial transient period and decreased with increasing the sliding velocity.