Abstract
The stability of mesoporous hydroxyapatite (HAP) powder was studied following treatments of ultrasound, pH and heating. HAP was found to be mechanically stable up to (and including) 1 h continuous ultrasonic treatment in water. The HAP structure was also stable to pH, evidenced by practically identical XRD and FTIR spectra over the pH range 2–12. The surface area increased progressively with increasing acidity, reaching a maximum of 121.9 m2 g−1 at pH 2, while alkaline conditions decreased the surface area to a minimum of 55.4 m2 g−1 at pH 12. Heating in air had a significant influence on the structural and morphological properties of HAP, which underwent dehydroxylation to form oxyhydroxyapatite (OHAP) at temperatures ≥ 650 °C, and β-tricalcium phosphate (β-TCP) ≥750 °C. The surface area decreased at elevated temperatures due to agglomeration of HAP crystals by sintering, which was associated with an increased particle size.
Highlights
Hydroxyapatite [Ca10(PO4)6(OH)2, HAP] is a stable apatite compound and has been used widely due to its similarity to human bone composition, biocompatibility and bioactivity [1]
The mechanical stability of HAP scaffolds, prepared by a sponge replica method, was evaluated by a uniaxial compression test, which calculates the strength of HAP by measuring the stress value at failure
The fact that we do not observe any changes in HAP using the soft-templated preparation method proves that this HAP is stable given the severity of 1 h ultrasonic treatment
Summary
Hydroxyapatite [Ca10(PO4)6(OH), HAP] is a stable apatite compound and has been used widely due to its similarity to human bone composition, biocompatibility and bioactivity [1]. Synthetic HAP is employed as a biomaterial for orthopaedic and dental replacements [2] Beside medical applications it has been applied in the field of heterogeneous catalysis as a support because of its bifunctionality, hydrophilic properties and high structural stability, as reviewed by Gruselle et al [3]. Other studies focused on the mechanical stability of HAP scaffolds for bio-medical applications. The results show that the HAP structure is mechanically robust, fully resistant to changes in pH, and stable upon heating in air to approximately 650 °C. These findings support the use of HAP in a range of applications
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