Synergistic strengthening and toughening of zircon ceramics by the additions of SiC whisker and 3Y-TZP simultaneously

The strengthening and toughening behaviours of SiC whiskers and tetragonal zirconia particles (3Y-TZP) in a zircon matrix iu were investigated The results showed that the addition of SiC whiskers or 3Y-TZP could improve mechanical properties to some extent. The flexural strength and fracture toughness of 30 vol% SiC(w)/ZrSiO4 reached 460 MPa and 4.7 MPa m(1/2), while the flexural strength and fracture toughness of 20 vol% SY-TZP/ZrSiO4 were 410 MPa and 4.3 MPa m(1/2). Furthermore, m when SiC whiskers and 3Y-TZP were introduced into the zircon matrix simultaneously, a drastic improvment in mechanical properties was achieved and a positive synergistic toughening effect was observed, showing that the combined toughening effect of SiC(w) and 3Y-TZP together was bigger than the sum of the individual toughening effects when either reinforcement acted alone. The flexural strength and fracture toughness of 30 vol% SiC(w)/20 vol% 3Y-TZP/ZrSiO4 were 580 MPa and 7.0 MPa m(1/2) at room temperature, which were 90% and 130% higher than those of monolithic zircon and could be maintained up to 800 degrees C. The microstructural observations by SEM and phase analysis by XRD demonstrated that the synergistic toughening effect was engendered from the interaction between microcrack toughening mechanism of 3Y-TZP and crack deflection, interfacial debonding as well as whisker pull-out by SIC whisker. (C) 1997 Elsevier Science Limited.