Controlling the pore characteristics of mesoporous apatite materials: Hydroxyapatite and carbonate apatite

Mesoporous hydroxyapatite (HA) and carbonated hydroxyapatite (CHA) were synthesised through the soft template route by using ionic surfactants, namely decyltrimethylammonium bromide (C10TAB) and hexadecyltrimethylammonium bromide (C16TAB), and non-ionic surfactants, namely P123 and F127. After calcination at 550 °C, a porous structure, with pore sizes varying from 2 nm to 49.2 nm and with a specific surface area ranging from 21 to 73 m2g−1, was formed with different surfactants. The axial view of the TEM images revealed that the pores formed within the particles were distributed randomly. The continuous pH-control technique and high water ratio may produce mesopores with better pore characteristics. Meanwhile, surfactants with a longer hydrophobic alkyl are expected to produce HA with larger pores but with a lower surface area. A higher surface area was observed for CHA synthesised with triblock co-polymers surfactants of a higher propylene oxide (PO) unit.