Mechanical properties and electrical conductivity of alumina/MWCNT and alumina/zirconia/MWCNT composites

The alumina/multi-wall carbon nanotubes (MWCNT) and Al2O3/ZrO2/MWCNT composites with up to 2 vol% of MWCNT were prepared and characterized. The homogeneity of the composite powders was ensured by application of freeze drying and granulation as a method for drying of stabilized aqueous suspensions. The soft spherical granules were hot pressed at 1500 °C for 2 h under uniaxial mechanical pressure of 30 MPa to prepare dense composites. The mechanical properties, namely Vickers hardness (HV1) and fracture toughness (K1c), together with DC electrical conductivity (σ) were measured, and compared with the pure alumina reference prepared under similar conditions. Incorporation of 1 vol% of the MWCNT into the alumina, and alumina/zirconia matrices (composites AC and AZC, respectively) lead to the increase of fracture toughness by 8% and 35%, in comparison to the monolithic alumina reference. The electrical conductivity increased from 10−12 S/m in the pure alumina to 2.7×10−1 S/m in the composites containing 2 vol% of the MWCNT.