Microstructure and mechanical properties of yttria-stabilized ZrO_2/Al_2O_3 nanocomposite ceramics

摘要

Yttria-stabilized ZrO_2/Al_2O_3 (abridged as YSZ/Al_2O_3 ) nanocomposite ceramics were prepared by pressureless sintering of the green sheets of the YSZ/Al_2O_3 nanopowders synthesized by co-precipitation method. The relative density, average grain size, and phase microstructure of the YSZ/Al_2O_3 nanoceramics as a function of YSZ contents were investigated. The relative densities of the YSZ/Al_2O_3 nanoceramics are over 95 percent as the YSZ contents of the YSZ/Al_2O_3 nanopowders are within 20-85 mol percent. The average grain sizes of the ZrO_2 and Al_2O_3 of the as-sintered YSZ/ Al_2O_3 nanoceramics decrease with increasing YSZ content of the co-precipitated YSZ/Al_2O_3 nanopowders, while the content of monoclinic ZrO_2 of YSZ/Al_2O_3 nanoceramics increases with increasing YSZ content. The presence of the second phase effectively li mits a rapid grain growth of the matrix alumina. The YSZ/Al_2O_3 nanoceramics with an average grain sizes below 80 nm, relative density over 95 percent, and hardness as high as 19.8 GPa were obtained by the pressureless sintering.