Synthesis of silicon-substituted hydroxyapatite using hydrothermal process

An alternative route for preparing silicon-substituted hydroxyapatite powders Ca-10(PO4)(6-x)(SiO4)(x)(OH)(2-x) (Si-HAp); using different content of SiO4 (0.588-0.48M) in the aqueous solution of Si precursor was investigated. Tetramethylammonium silicate (TMAS) was used as a silicon precursor. The experiments were carried out via conventional hydrothermal treatments at 150 degrees C for 10 h. The Si-HAp nanoparticles obtained were characterized by X-ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR), inductively coupled plasma AES (ICPAES) and scanning electron microscopy (SEM) techniques. A drastically decrease of the diffraction was not observed by increasing the Si content in the structure of the hydrothermally Si-Hap particles produced. A detailed structural analysis conducted by Rietveld refinement indicated that the incorporation of Si occurred in hydroxyapatite (HAp) lattice by partially replacing phosphate (PO43-) groups with silicate (SiO44-) groups. Raman and X-ray photoelectron spectroscopy (XPS) analysis confirmed the substitution of PO43- by SiO(4)(4- )in the Si-HAp structure. The crystallite size decreases by increasing the Si molar content in the hexagonal HAp structure. TEM observations revealed that the Si-HAp produced have a high crystallinity. A slight decrease of the particle size of the Si-HAp compared to pure HAp was observed (from 60-100 nm to 40-70 nm). The morphological analysis revealed that all the SiHAp powders prepared have the rod-like shape. Additionally, a slight decrease in both length and diameter of nanorods was observed by increasing the silicon content, the minimum size obtained for the powders containing the largest amount of Si (20Si-HAp) 25 and 70 nm. The presence of Si in the structure of the Si-HAp favored densification of the compacts treated at high temperature 1200 degrees C in comparison with pure HAp. Published by Elsevier Espana, S.L.U. on behalf of SECV.