Additively Manufactured Biowaste-Derived Hydroxyapatite Bioceramics

Yap, Jyen Hong (2025) Additively Manufactured Biowaste-Derived Hydroxyapatite Bioceramics. Masters thesis, Tunku Abdul Rahman University of Management and Technology.

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Abstract

Hydroxyapatite (HA), a naturally occurring calcium phosphate salt, constitutes about 60% of bone composition in animal bodies. Its excellent biocompatibility makes it a popular bioceramic for bone grafting in the medical industry. HA can be synthesised chemically or extracted from natural sources via calcination of bone waste. However, its porous nature leads to poor mechanical properties, limiting its use in synthetic bone grafts. This research aims to advance additive manufacturing of dense ceramic products by utilising powdery HA, focusing initially on the synthesis process. Raw bone powder was assessed by thermogravimetric analysis (TGA). Powders were calcined (800 - 1000 °C) and sintered (1200 - 1350 °C) for the assessment of mechanical performances, using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), nitrogen adsorption for Brunauer-Emmett-Teller (BET) surface area, and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). Spectra and patterns showed dominant HA features with β-tricalcium phosphate (β-TCP) present as a secondary phase across calcination conditions, and powder Ca/P ratios of 1.53 - 1.58. Optimal consolidation occurred at 900 °C calcination and 1250 °C sintering, and the optimised synthesis was subsequently applied to fused deposition modelling (FDM) feedstock at 70 vol.%. In HDPE-based feedstock formulations, FDM printed HA parts achieved ~97.0 % relative density and 4.98 GPa hardness, comparable to compacted HA samples; fracture toughness was slightly lower at ~1 MPa·m1/2. Building on the optimised HA processing route, zinc incorporation was evaluated at a solid loading of 60 vol.% to investigate the effect of Zn addition on mechanical integrity of FDM printed HA. At 0.5 mol% Zn, Zn-incorporated HA produced 3D-printed specimens with approximately 96.7 % relative density, 5.01 GPa Vickers hardness, and 1.28 MPa·m1/2 fracture toughness, representing a marginal enhancement relative to undoped HA processed under identical conditions. These results indicate that low-level Zn addition can modestly improve mechanical performance in FDM-fabricated HA while maintaining high densification, suggesting potential for load-bearing medical applications.