Mechanical properties of bovine hydroxyapatite (BHA) composites doped with SiO2, MgO, Al2O3, and ZrO2
Biologically derived hydroxyapatite from calcinated (at 850 °C) bovine bones (BHA) was doped with 5 wt% and 10 wt% of SiO2, MgO, Al2O3 and ZrO2 (stabilized with 8% Y2O3). The aim was to improve the sintering ability and the mechanical properties (compression strength and hardness) of the resultant BHA-composites. Cylindrical samples were sintered at several temperatures between 1,000 and 1,300 °C for 4 h in air. The experimental results showed that sintering generally occurs at 1,200 °C. The BHA–MgO composites showed the best sintering performance. In the BHA–SiO2 composites, extended formation of glassy phase occurred at 1,300 °C, resulting in structural degradation of the resultant samples. No sound reinforcement was achieved in the case of doping with Al2O3 and zirconia probably due to the big gap between the optimum sintering temperatures of BHA and these two oxides.
KeywordsZirconia Y2O3 Compression Strength Bovine Spongiform Encephalopathy Extensive Formation
This study was carried out with the financial support of the Turkish Republic Government Planning Organization in the framework of the Project “Manufacturing and Characterization of Electro-Conductive Bioceramics” with project number 2003 K120810. S. Agathopoulos gratefully acknowledges his financial support through the Project ENTER 04EP26 of the European Union and the Greek Secretariat of Research and Technology. SEM pictures were taken under supervision of Associate Professor Ahmet Capoglu from Gebze Institute of Technology. The authors thank to Associate Professor Dr. G. Goller from Istanbul Technical University for using the microhardness apparatus.
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