GOALI: Rapid Sintering to Manufacture Fully Dense and Bioactive Nanoscrystalline Hydroxyapatite

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This research effort explores a short time densification process - termed Field Assisted Sintering Technique (FAST) - to manufacture fully dense nanocrystalline hydroxypaptite (HA) ceramic parts. First, the fundamental factors governing the FAST processing of nanocrystalline HA ceramics will be established. The relationship between processing parameters (electrical, pressure, sintering environment, and kinetic) and the resulting structure and properties of dense HA parts will be investigated. Next, mechanical properties and biocompatibility of fully dense HA ceramics as a function of sintering conditions will be determined. Finally, the FAST process will be used to manufacture near net shape nanocrystalline HA orthopedic implants. The mechanical and in vivo properties of these dense parts will be validated. Our industrial partner, Angstrom Medica (AM) in Woburn (MA), will contribute HA nanopowders, will design the real orthopedic implants for net shape manufacturing, and test the dense calcium phosphate ceramics for in-vitro biocompatibility. If successful, the results of this research will be used to develop a technology to efficiently manufacture orthopedic implants with improved mechanical and biological properties. The proposed work will create the engineering foundations on which a new FAST manufacturing practice may be based. FAST sintering process enables densification of HA powders in minutes, as compared to hours in the currently used hot pressing process, thus enhancing the processing productivity. The net shape formability of this process will be adapted to manufacture orthopedic implants in shorter time and with a reduced number of processing steps. The retention of nanocrystallline structure in the final HA material has a high potential to produce implants with superior mechanical and biological properties that expedite healing, and reduce pain and inflammation upon surgery. The evaluation of process dependent microstructure and its relationship to these final properties will be an integral component of manufacturing reliable HA orthopedic implants.