Nano to micro size transition of hydroxyapatite in porcine bone during heat treatment with low heating rates

• Published in: Progress in natural science 2020-08, Vol.30 (4), p.494-501
• Main Authors: Castillo-Paz, Angélica M., Londoño-Restrepo, Sandra M., Tirado-Mejía, Liliana, Mondragón, M.A., Rodríguez-García, Mario E.
• Format: Article
• Language: English
• Subjects: Bone composition; Hydroxyapatite nanoparticles; Mineral composition; Porosity formation; Raman analysis
• ISSN: 1002-0071
• DOI: 10.1016/j.pnsc.2020.06.005

This work focuses on the changes of raw hydroxyapatite obtained from porcine bones during heat treatment with heating rates of 2.5 and 5.0 °C/min between 600 °C and 1100 °C. High-Resolution transmission electron microscopy (HR-TEM) images showed that raw hydroxyapatite was formed by high-ordered nanometric platelet crystals with a length of around 18 nm and width around 7 nm. High-Resolution scanning electron microscopy (HR-SEM) images evidenced the coalescence phenomena during heating giving. It was found that the growth of the crystals and the transition from nano to a micro-size occurred at around 700 °C. And the changes in the full width at half maximum (FWHM) for the characteristic (002) plane of the X-ray diffraction patterns and the FWHM of the characteristic Raman band at 960 cm-1 for ν1 PO43- exhibited the transition from nano to a micro size, that was confirmed by HR-SEM images and the thermogravimetric (TG) analysis. The porosity of the BIO-HAp changes from intra nanometric to intercrystalline. [Display omitted] •Porcine hydroxyapatite (P-HAp) crystals remain nanometric when calcination until 700 °C.•P-HAp exhibits a nano to micro size transition at 700 °C.•Until 700 °C, porosity is due to intra nanocrystal spaces; after that, it is caused by inter microcrystal spaces.•Samples calcined until 700 °C exhibit broad XRD peaks because of the nanometric size of P-HAp crystals.