The PhD research described within this thesis involved the fabrication of micro-porous Hydroxyapatite (HA)/tri-calcium phosphate (TCP) and zirconia composites by using a newly developed slip-deposition and coating/substrate co-sintering process. The integration of mechanical and biological requirements is a challenge in developing porous HA and TCP scaffold for load-bearing implant applications. The bending strength of the composites with HA/TCP coatings developed in this study is over 300 MPa, which is over the bending strength of natural compact bones. HA/TCP based scaffold coatings have multiple scale porous structures with pore size ranging 1 to 10 μm and 20 to 50μm. The thickness of the coating was from 50 μm to over 1mm. A Freeze drying method has also been introduced with the slip deposition method to create macro porous thick coatings. The coating thickness developed by the freeze drying method was around 1 to 2 mm. The pore size ranges from 50 to 500μm. Two research designs were considered here (i) strength does not have to come from the HA scaffold. (ii) HA scaffold coating of certain thickness developed on a strong substrate will have the same function of a porous scaffold. Focused ion beam (FIB) micrographs show most of the micro pores in the HA/TCP coatings are interconnected. Micro indentation and primarily adhesive strength tests demonstrate that the scaffold coating strongly bonds with the zirconia-based substrate. In vitro cell culture study indicates that the HA/TCP coatings are bio-active just as common HA scaffolds. It is evident that the strong layered scaffold-like hydroxyapatite-zirconia composites may offer new implant options for bone reconstructions requiring immediate load bearing capacity. The Thesis consists of four main parts (1) Fabrication of micro-porous HA coating on strong zirconia substrate (Chapter 3), (2) Mechanical properties and In Vitro results of this composite (Chapter 4), (3) Coating/substrate interface analysis by using the FIB method (Chapter 5), (4) Fabrication of thick macroporous coating by freeze drying method (Chapter 6).
|Qualification||Doctor of Philosophy|
|Publication status||Unpublished - 2014|