Effects of Solute and Surfactant Addition on the Crystallization and Morphology of Hydroxyapatite Powders Synthesized by Hydrolysis of Calcium Hydrogen Phosphate Dehydrate (DCPD)

The effects of the addition of alcohol and cetyltrimethylammonium bromide (CTAB) on the crystallization and the morphology of hydroxyapatite (HA) powders synthesized by hydrolysis of calcium hydrogen phosphate dehydrate (DCPD) in the 2.5 M NaOH solutions at 348 K (75 °C) for 1 hour have been studied. The values of zeta potential have large differences between the sums of DCPD with CTAB (Z _DCPD+CTAB) minus the sum of DCPD and CTAB (Z _DCPD + Z _CTAB), and of HA with CTAB (Z _HA+CTAB) minus the sum of HA and CTAB (Z _HA + Z _CTAB), respectively. When the hydrolysis of DCPD occurred in the 2.5 M NaOH solutions at 348 K (75 °C) for 1 hour both with and without alcohol and CTAB, XRD results show the only one phase of HA in the as-dried powders. When the NaOH solution does not contain CTAB, the crystallite size of HA powders decreased from 23 ± 1 to 16 ± 1 nm as the alcohol content was more than 50 pct. The crystallite size of HA powders obtained from DCPD synthesized in the 2.5 M NaOH solution with 1.0 × 10⁻³ M CTAB decreased when the alcohol content was increased to 70 pct, whereas the crystallite size increased when the alcohol concentration was greater than that of 70 pct. SEM images show that the HA powders have a rod-like shape when DCPD was synthesized in the 2.5 M NaOH solution without CTAB or alcohol. When the NaOH solution had 1.0 × 10⁻³ M CTAB and various alcohol concentrations, the morphology of HA powder still maintained a rod-like or needle-like shape. The HA powder had a maximum specific surface area of 180.25 m²/g when the hydrolysis of DCPD occurred in a 2.5 M NaOH solution containing 1.0 × 10⁻³ M CTAB and 70 pct alcohol at 348 K (75 °C) for 1 hour.