Novel route for rapid sol-gel synthesis of hydroxyapatite, avoiding ageing and using fast drying with a 50-fold to 200-fold reduction in process time


We have developed an innovative, rapid sol-gel method of producing hydroxyapatite nanopowders that avoids the conventional lengthy ageing and drying processes (over a week), being 200 times quicker in comparison to conventional aqueous sol-gel preparation, and 50 times quicker than ethanol based sol-gel synthesis. Two different sets of experimental conditions, in terms of pH value (5.5 and 7.5), synthesis temperature (45 and 90 degrees C), drying temperature (60 and 80 degrees C) and calcination temperature (400 and 700 degrees C) were explored. The products were characterised by X-ray diffraction (XRD) Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and specific surface area (SSA) measurements. Pure hydroxyapatite (Ca-10(PO4)(6)(OH)(2), HAp) was obtained for the powders synthesised at pH 7.5 and calcined at 400 degrees C, while biphasic mixtures of HAp/beta-tricalcium phosphate ((beta-Ca-3(PO4)(2), TCP) were produced at pH 5.5 and (pH 7.5 at elevated temperature). The novel rapid drying was up to 200 times faster than conventional drying, only needing 1 h with no prior ageing step, and favoured the formation of smaller/finer nanopowders, while producing pure HAp or phase mixtures virtually identical to those obtained from the slow conventional drying method, despite the absence of a slow ageing process. The products of this novel rapid process were actually shown to have smaller crystallite sizes and larger SSA, which should result in increased bioactivity. (C) 2016 Elsevier B.V. All rights reserved.




Materials Science


Ben-Arfa, BAE; Salvado, IMM; Ferreira, JMF; Pullar, RC

nossos autores


R.C. Pullar was supported by the Fundacao para Ciencia e Tecnologia (FCT) [grant SFRH/BPD/97115/2013] for this work. This work was developed in the scope of the project CICECO-Aveiro Institute of Materials [FCT UID/CTM/50011/2013], financed by national funds through the FCT/MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement.

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