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Processing and Mechanical Properties of C-Nanotube Reinforced Alumina Composites

2008; Wiley; Linguagem: Inglês

10.1002/9780470294628.ch77

1940-6339

Sekyung Chang, Robert H. Doremus, Pulickel M. Ajayan, Richard W. Siegel,

Tribology and Wear Analysis

Alumina and alumina matrix composites containing 5 to 20 volume percent of multi-wall carbon nanotubes (MWNT) were fabricated by hot pressing in Ar atmosphere at 1300°C for 1h with 60 MPa of applied pressure. A powder of α-phase alumina, with 44 nm mean diameter, and arc-derived MWNT were used for these experiments. The composite sintered to nearly full density. Hardness and fracture toughness were measured using the Vickers indentation method and these values were compared to those for monolithic alumina. The hardness of the composite decreased with increasing volume content of the MWNT. Hardness of the composite containing 20 vol. % of MWNT dropped to 13.6 GPa, but its value was 3 GPa higher than that of a composite containing the same volume percent of graphite. The fracture toughness for the composite containing 10 vol. % of the MWNT was 4.2 MPa.m0.5; an improvement of 24 % when compared with that of the monolithic alumina. Weak bonds between the MWNT and the alumina matrix, pullout of the MWNT without breaking, and crack deflection at the interface are possible mechanisms leading to the improvement of the fracture toughness.