| Hydroxyapatite (HA) ceramic has attracted much attention due to its superior biocompatibility and bioactivity as a substitute material in bone grafting. However, its clinical applications are limited to free of high load-bearing situations due to its poor mechanical strength. In this project, nano-HA ceramic composites with improved mechanical strength and comparatively high bioactivity were fabricated for different load-bearing applications in bone tissue engineering.;Nano-sized HA particles were synthesized in the first step to mimic HA in natural bone. Ultrasonic vibration was introduced in the co-precipitation synthesizing process, which provided more nucleation energy for the HA crystals, improved the nucleation density and consequently refined the HA crystals. Surfactant cetyltrimethyl-ammonium bromide (CTAB) was introduced in the fabricating process to improve dispersing properties. Nano-size needle-like HA particles were fabricated with the aid of ultrasonic vibration and surfactant.;Multi-wall carbon nanotubes (MWNTs) were chosen as the reinforcing phase due to their unique mechanical properties and superior biocompatibility. In this study, the surfaces of MWNTs were modified to improve their dispersion property. The flexural strength and toughness of the fabricated nano-HA-MWNT composites with 7vol% MWNTs reached 103MPa and 1.28 MPa·m1/2 , which were improvement about 34% and 51% compared with those of unmodified HA ceramics.;HA-ZrO2-MWNT composites were designed and fabricated to further improve the mechanical strength of HA ceramics. The flexural strength and the toughness of the HA-ZrO2-MWNT composites reached 183 MPa and 2.20 MPa·m1/2 which were close to those of cortical bone, when the volume percentages of the reinforcing phases of Zr02 and MWNTs were 27vo1% and 7vol%, respectively. The in-vitro method was used to test the bioactivity of the composites. The surfaces of the HA-MWNT samples were covered by a new growth layer after immersion for 3 days. The EDX results showed that the covered layer was calcium phosphate material. The results indicated that both HA-MWNT and HA-ZrO2-MWNT composites had comparatively high bioactivity.;Finite element models were constructed to study the reinforcing effects of MWNT5 In addition, a load bearing case for a dental implantation was also studied using the finite element method to explore the applicability of the HA composites. |
