This study investigated the consolidation of hydroxyapatite (HAp) ceramics with different graphene oxide (GO) contents (0–1.00 wt.%) via the Cold Sintering Process (CSP), aiming to evaluate their effects on densification, mechanical properties, thermal stability, and microstructure [1]. CSP was performed at 200 °C under 300 MPa using diluted phosphoric acid as a transient liquid phase. Vickers hardness, fracture toughness, flexural strength, SEM/EDS, TGA/DSC, XRD with Rietveld refinement, FTIR, and Raman spectroscopy were employed for characterization.

GO addition increased the relative density from ~84.7% (pure HAp) to ~87.3% (HAp1.00GO), with the best mechanical performance observed for HAp0.50GO, which showed a hardness of 2.81 GPa, fracture toughness of 0.77 MPa·m⁰·⁵, and flexural strength of 51.63 MPa—up to 79% higher than pure HAp. These improvements were attributed to the lamellar morphology and oxygenated functional groups of GO, which promoted chemical interactions with dissolved HAp ions, enhancing precipitation-driven densification and interparticle cohesion [2].

Morphological analysis revealed that HAp0.50GO exhibited the most homogeneous and dense microstructure with well-formed interparticle bridges, while higher GO contents (0.75–1.00 wt.%) led to agglomeration and heterogeneity, impairing mechanical performance [3].

Thermal analysis indicated that GO incorporation improved thermal stability and reduced degradation related to β-TCP formation. XRD confirmed the preservation of the crystalline HAp phase in all compositions, with no secondary phases detected. Rietveld refinement showed decreased crystallite size and increased specific surface area for intermediate GO contents (0.25 and 0.50 wt.%), suggesting higher surface reactivity and potential bioactivity [4].

FTIR confirmed the preservation of HAp’s chemical structure, while Raman spectroscopy detected D and G bands from GO in samples with ≥0.50 wt.%, confirming its incorporation and revealing variations in carbon structural order with increasing GO content. The lowest ID/IG ratio (0.57) for HAp0.75GO indicated greater graphitic order, whereas HAp1.00GO displayed the highest disorder (ID/IG = 0.92), likely due to agglomeration.

Overall, the optimal GO content was ~0.50 wt.%, balancing densification, microstructural integrity, mechanical strength, and thermal stability without compromising crystallinity. These results demonstrate the feasibility of producing HAp/GO ceramics via CSP at low temperature with enhanced properties for advanced biomedical applications, such as synthetic bone grafts with improved mechanical resistance and stability [5].