PREPARATION AND CHARACTERIZATION OF HA POWDERS, DENSE AND POROUS HA BASED COMPOSITES

The Aim, the Signaficance, and the Expected Outcomes of the Project:
     The necessity for replacing bone substance which has been lost for various reasons have been the subject of an intensive research effort worldwide over the last 30 years. Hydroxyapatite(HA) is the major inorganic constituent of natural bone. HA based materials offer significant advantages over other implant materials like various metals, ceramics and polymers due to their biocompatibility and bioactivity. Unfortunately, due to their relatively poor mechanical properties, dense pure HA based materials can only be used as small unloaded implants , powders and coatings. Research on improving the mechanical reliability of HA based hard tissue implant materials have been concentrated on various composite materials. Ceramic particle and HA whisker reinforced HA based composite materials attracted significant interest recently.The preparation and characterization of HA whisker reinforced HA based ceramic materials will be investigated in this project. Commercial HA powders along with powders precipitated with a number of techniques will be used for the preparation of pure HA green structures. The densification behaviour of these structures will be investigated in the 1000-1400^oC range. HA whiskers will be synthesized by using hydrothermal and flux methods. Composite materials with 0-40 vol.% whiskers will be consolidated by using slip casting and dry presing. The densification behaviour of these materials in the above temperature range will be determined. The greeen-sintered structures will be characterized for their densities, pore structures. Optic Microscopy, SEM will be used for microstructure characterization. XRD will be used for phase analyses. The microhardness and mechanical properties of the sintered structures will be determined and correlated to the starting powders-whiskers and the microstucture. The results of this work is expected to contribute to the knowledge on the preparation and characterization of these potential hard tissue implant composite materials.