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

authors	Ben-Arfa, BAE; Salvado, IMM; Ferreira, JMF; Pullar, RC
nationality	International
journal	MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS
author keywords	Hydroxyapatite; beta-TCP; Nanoparticles; Nano-synthesis; Biocompatibility; Sol-gel
keywords	MECHANOCHEMICAL SYNTHESIS; PRECIPITATION PROCESS; CHEMICAL-SYNTHESIS; POWDERS; PHOSPHATE
abstract	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.
publisher	ELSEVIER SCIENCE BV
issn	0928-4931
year published	2017
volume	70
beginning page	796
ending page	804
digital object identifier (doi)	10.1016/j.msec.2016.09.054
web of science category	Materials Science, Biomaterials
subject category	Materials Science
unique article identifier	WOS:000388046900093