Sintering effects on chemical and physical properties of bioactive ceramics

• Published in: Journal of advanced ceramics 2013-09, Vol.2 (3), p.274-284
• Main Authors: Witek, Lukasz, Smay, James, Silva, Nelson R. F. A., Guda, Teja, Ong, Joo L., Coelho, Paulo G.
• Format: Article
• Language: English
• Subjects: Biocompatibility; Calcination; Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composites; Glass; Hydroxyapatite; Inductively coupled plasma; Materials Science; Mechanical properties; Nanotechnology; Natural Materials; Pastes; Physical properties; Porosity; Research Article; Sintering; Sintering (powder metallurgy); Structural Materials
• ISSN: 2226-4108; 2227-8508; 2227-8508
• DOI: 10.1007/s40145-013-0072-y

The objective of this study was to characterize the chemical and physical properties of bioactive ceramics prepared from an aqueous paste containing hydroxyapatite (HA) and beta tri-calcium phosphate (β-TCP). Prior to formulating the paste, HA and β-TCP were calcined at 800 °C and 975 °C (11 h), milled, and blended into 15%/85% HA/β-TCP volume-mixed paste. Fabricated cylindrical rods were subsequently sintered to 900 °C, 1100 °C or 1250 °C. The sintered specimens were characterized by helium pycnometry, X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), and inductively coupled plasma (ICP) spectroscopy for evaluation of porosity, crystalline phase, functional-groups, and Ca:P ratio, respectively. Mechanical properties were assessed via 3-point bending and diametral compression. Qualitative microstructural evaluation using scanning electron microscopy (SEM) showed larger pores and a broader pore size distribution (PSD) for materials sintered at 900 °C and 1100 °C, whereas the 1250 °C samples showed more uniform PSD. Porosity quantification showed significantly higher porosity for materials sintered to 900 °C and 1250 °C ( p < 0.05). XRD indicated substantial deviations from the 15%/85% HA/β-TCP formulation following sintering where lower amounts of HA were observed when sintering temperature was increased. Mechanical testing demonstrated significant differences between calcination temperatures and different sintering regimes ( p < 0.05). Variation in chemical composition and mechanical properties of bioactive ceramics were direct consequences of calcination and sintering.