Fabrication of carbon nanofiber(CNF)-dispersed Al2O3 composites by pulsed electric-current pressure sintering and their mechanical and electrical properties.

Dense Al₂O₃-based composites (≥99.0% of theoretical) dispersed with carbon nanofibers (CNFs) were fabricated using the pulsed electric-current pressure sintering (PECPS) for 5 min at 1300°C and 30 MPa in a vacuum. The dispersion of CNFs into the matrix depended much on the particle size of the starting Al₂O₃ powders. Mechanical properties of the composites were evaluated in relation with their microstructures; high values of three-point bending strength σ_b (∼800 MPa) and fracture toughness K _IC (∼5 MPa·m^1/2) were attained at the composition of CNF/Al₂O₃ = 5:95 vol%, which σ_b and K _IC values were ∼25% and ∼5%, respectively, higher than those of monolithic Al₂O₃. This might be due to the small Al₂O₃ grains (1.6 μm) of dense sintered compacts compared with that (4.4 μm) for the pure Al₂O₃ ceramics, resulting from the suppression of grain growth during sintering induced by uniformly dispersed CNFs in the matrix. Electrical resistivity of CNF/Al₂O₃ composites decreased rapidly from >10¹⁵ to ∼2.1 × 10⁻² Ωm (5vol%CNF addition), suggesting the machinability of Al₂O₃-based composites by electrical discharge machining. [ABSTRACT FROM AUTHOR]