Preparation of MWNTs/Al₂O₃ composites and their mechanical and electrical properties

The mechanical and electrical properties of MWNTs/Al₂O ₃ composite prepared fabricated by hot pressing are investigated. The relation between properties and microstructure of composites is also discussed. With 4wt% MWNTs as reinforcement, the fracture toughness of composite obtained reaches 5.55 MPa·m^1/2, which is 80% higher than that of pure Al₂O₃ obtained in the same conditions. The main toughening mechanism is CNTs' pinning alumina grain boundaries, and the pullout of CNTs takes effect also. Through adding 2wt% MWNTs and altering the mix method, the fracture toughness of the composite obtained is 3.97 MPa·m^1/2. Furthermore, the electrical resistivity is as low as 8.4×10^-3 Ω-m, decreasing by 14 orders of magnitude compared with pure alumina ceramics. The function of CNTs in composite is related to the distribution state of CNTs in composite, and the distribution state of CNTs in matrix is dependent on preparation procedures. Copyright by Science in China Press 2005.