Abstract
Whisker-like hydroxyapatite (HAp) was synthesized by an aqueous ammonia neutralization method using nitrogen carrier. Acidic-aqueous solutions containing 0.167 mol·dm-3 Ca(NO3)2 and 0.1 mol·dm-3 (NH4)2HPO4 were heated at three different temperatures (70°C, 75°C and 80°C) for 24h and then at 95°C for 24h; during this process the solutions were neutralized with nitrogen-carrier gases saturated with various concentrations of aqueous ammonia. The flow rate of nitrogen carrier was 0.1 dm3·min-1. The obtained whisker-like HAp had Ca/P ratios of 1.59 to 1.62, which were non-stoichiometric compositions. The products were whisker-like and/or tape-like and/or acicular crystals. In the above three conditions, the mean values of long-axis size distribution and aspect ratio of whisker-like HAp were 14.5μm and 14.2 at 70°C, 18.1μm and 19.3 at 75°C, and 12.9μm and 13.2 at 80°C, respectively.
