Homogeneous fabrication and densification of zirconia-toughened alumina (ZTA) composite by the surface-induced coating

Abstract

This article proposes a new scheme for fabricating homogeneous Al2O3–ZrO2 composite, in which a thermodynamic theory of interfacial electrochemical phenomena is applied. The theory predicts that a heterogeneous Al2O3 interface in colloidal dispersion can induce an enhanced concentration of the ionic species needed for a selective formation of the ZrO2 precursor at the Al2O3/aqueous solution interface. Based on this proposition, a homogeneous Al2O3–ZrO2 composite powder was fabricated by a surface-induced coating of the fine ZrO2 precursor on the kinetically stable colloid particles of Al2O3. The composite prepared by the surface-induced coating was characterized by a uniform spatial distribution of the dispersed ZrO2 phase and by the absence of large ZrO2 grains formed from hard ZrO2 agglomerates. The composite also showed highly uniform grain size distribution of both the dispersed ZrO2 and the matrix Al2O3 phases. The uniform grain size distribution of the matrix phase indicates that the homogeneous coating of the fine ZrO2 particles is effectively pinning the Al2O3 grain boundaries.