FABRICATION AND FRACTURE PROPERTIES OF ALUMINA MATRIX COMPOSITES REINFORCED WITH CARBON NANOTUBES

Abstract

In this study, alumina matrix composites reinforced with carbon nanotubes (CNTs) were fabricated by ultrasonic dispersion, ball milling, mixing, compaction, and sintering processes, and their relative density, electrical resistance, hardness, flexure strength, and fracture toughness were evaluated. 0 similar to 3 vol.% of CNTs were relatively homogeneously dispersed in the composites in spite of the existence of some pores. The three-point bending test results indicated that the flexure strength increased with increasing volume fraction of CNTs, and reached the maximum when the CNT fraction was 1.5 vol.%. The fracture toughness increased as the CNT fraction increased, and the fracture toughness of the composite containing 3 vol.% of CNTs was higher by 40% than that of the monolithic alumina. According to observation of the crack propagation path after the indentation fracture test, a new toughening mechanism of grain interface bridging-induced CNT bridging was suggested to explain the improvement of fracture toughness in the alumina matrix composites reinforced with CNTs.