Synthesis and Sintering of Bio-Waste Derived Hydroxyapatite

Teoh, Min Wei (2024) Synthesis and Sintering of Bio-Waste Derived Hydroxyapatite. Masters thesis, Tunku Abdul Rahman University of Management and Technology.

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Abstract

Hydroxyapatite (HA) is widely recognised as a favoured biomaterial for creating implants and bone grafts due to its exceptional biocompatibility and remarkable similarity to human bone. Despite high strength, low weight properties of metallic implants, the occurrence of inflammatory complications is unavoidable by some of the metallic implants. Additionally, the cost of synthesising the synthetic HA is generally considered unaffordable and the chemicals used is dangerous. Hence, there is a potential in utilising biowaste as an alternative source for obtaining HA and pectin, rather than relying on chemical methods. These natural sources encompass valuable elements that are not typically present in synthetic HA, thereby contributing to the enhanced biocompatibility of HA. This study aims to determine the physiochemical and mechanical properties of HA derived from chicken bones (CHA) through calcination. Pectin was extracted from orange peels via microwave irradiation, and 1 and 3wt% of pectin were respectively incorporated into the HA. The chicken bone-derived HA (CHA) was also ball milled for 30 to 180 minutes. The resulting powders were then pressed into disc samples before being sintered at temperatures of 1050, 1150, 1250 and 1350°C for two hours. Two-step sintering was also performed to compare the properties of HA with conventional sintering. Various analytical techniques, including Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), density measurement, and Vickers microhardness tests, were conducted to evaluate the characteristics and mechanical properties of the samples. The incorporation of pectin and ball milling did not interfere with the pure phases of HA, and minimal amounts of β-tricalcium phosphate (β-TCP) were detected in the XRD diffractograms. HA peak intensity reduced significantly while β-TCP peak intensity increased much when CHAs were conventionally sintered at 1350℃. Both the ball milling method and the addition of pectin effectively reduced the particle size of HA. However, the addition of pectin above 1wt% did not contribute significantly to the densification and hardness of CHA, compared to ball-milled CHA samples. The maximum relative density achieved was approximately 95.36%, and the Vickers microhardness reached 4.36 GPa for 90 min-ball milled CHA samples sintered at 1250°C. It was observed that the sintering temperature and ball milling had a more pronounced effect on the densification and hardness of CHA compared to the addition of pectin.