Effects of the buffer solutions on the growth of hydroxyapatite whiskers

Hydroxyapatite whiskers hare been synthesized by the precipitation reaction of the buffer solutions of calcium acetate and phosphoric acid (or phosphate) under pH 1-5 at 90 degrees C. Because the CH3COO- ions were able to neutralize the H+ ions released from the precipitation reaction, the precipitation of monetite, that causes a considerable decline of the pH of the solution during the reaction, could be prevented and the efficiency to obtain hydroxyapatite whiskers was improved by up to about 30 times compared with a non-buffer solution. By adjusting the concentrations and the Ca/P molar ratio of the solutions, hydroxyapatite whiskers with length from about 30 mu m to 300 mu m were obtained. The Ca/P atomic ratios of HAp whiskers in creased with increasing the Ca/P molar ratio or the PH of the solution, and varied from 1.60 to 1.66.