Processing and mechanical properties of hydroxyapatite pieces obtained by the gelcasting method

Abstract The aim of this work was to prepare hydroxyapatite (HA) pieces, by the gelcasting method, with appropriate mechanical properties for using as bone implants. The mechanical properties of the obtained pieces were evaluated. The influence of the solid content on the rheological behaviour of the slurries and, in turn, on the mechanical properties, was investigated. Pieces were prepared by using slurries containing 55 and 60 vol.% of an HA calcined at 1200 °C and 47 vol.% of HA calcined at 1100 °C. HA powders calcined at lower temperature than 1100 °C were not suitable for producing concentrated slurries. The raw and calcined HA were characterised by XRD, FTIR, X-ray fluorescence and elemental analysis. The pieces sintered at different temperatures and times were characterised by XRD, and the sintering treatment applied to the specimens for mechanical testing (1300 °C for 24 h) was selected taking into account the phases present after sintering. The mechanical properties of the green bodies were higher than obtained by other methods and the ones of the final pieces were comparable to those obtained by other techniques. The results indicated that slurries with a solid content higher than a limit value (for which limited contraction occurs) must be used and that the rheological properties of the slurries play an important role in the mechanical properties of the resulting pieces.