Composite materials with ZrO 2 –TiO 2 matrix and ZrO 2 containing ceramic fibres

Abstract

The aim of the work reported in the present paper was to obtain composites consisting of a ZrO₂–TiO₂ matrix reinforced with ceramic fibres containing 12 wt-% ZrO₂, which are resistant to temperatures higher than1500°C. The resulting ceramic matrix consisted of 95 wt-% ZrO₂, partially stabilised with CaO, and 5 wt-% rutile TiO₂. A ceramic fibre content of 0·82 vol.-% was used and for the matrix, several grades of ZrO₂ partially stabilised with CaO were explored, prepared by dry and wet grinding for various grinding periods. Composites were prepared by uniaxial die pressing at 350 MPa and sintered at two temperatures: 1360°C for 1 h and 1500°C for 3 h. The resulting composites showed the following range of properties: total drying and firing shrinkage 0·4–3·3%; apparent density 3·51–3·96 g cm^-3; porosity 25–34%; water absorption 6–10%; bend strength 12–43 MPa. The optimum ZrO₂ grades were determined based on physical and mechanical properties, and on structural determinations carried out by thermodifferential and thermogravimetric analyses, X-ray diffraction (XRD), and scanning electron microscopy (SEM). SEM evaluation illustrated the increase in average size of crystallites typical of ZrTiO₄ solid solution as a function of temperature, from 2 μm at 1360 up to 14 μm at 1600°C, and of their tendency to sinter.