Characterisation and mechanical testing of hydrothermally treated HA/ZrO(2) composites

Hydrothermal treatment is traditionally employed to improve the sinterability of powder compacts by reducing porosity and increasing apparent density. The effect of hydrothermal treatment on green powder compacts has been assessed in order to better understand how treatment may affect the sinterability of the bodies. Laboratory synthesised nano sized hydroxyapatite (HA) and a commercial zirconia (ZrO(2)) powder have been ball milled together to create composite mixtures containing 0-5wt% ZrO(2) loadings. Disc shaped bodies have been formed using uniaxial and subsequent isostatic pressure. The resultant coherent samples were subjected to hydrothermal treatment at either 120 or 250'C for 10h in order to assess the effect of this processing technique on the physical, mechanical and microstructural properties of the green composites. ZrO(2) loadings up to 3wt% increased apparent density from 90 to 92%, whereas increased loading to 5wt% increased flexural strength, from 6 to 9MPa. Increasing the hydrothermal treatment temperature increased open porosity, from ~44 to ~48% and reduced biaxial flexural strengths of the treated bodies compared to those of their room temperature isostatically pressed counterparts (~10 to ~6MPa).