Low temperature synthesis of hydroxyapatite ceramics from octacalcium phosphate by hydrothermal hot pressing

This study is to utilize a hydrothermal hot-pressing technique and prepare hydroxyapatite ceramics. The starting powder OCP (Ca8H2(PO4)(6).5H(2)O) and ammonia water were heated to 300degreesC at a rate of 10degreesC/min, and sintered under 40MPa for 2h. The effects of the amount and concentration of ammonia water were investigated. The results show that OCP reacted with NH4OH and produced HAp; the high concentration of ammonia water is advantageous for the solidification of the ceramics. The density, fracture toughness, and tensile strength of the ceramics that prepared with 10% high concentration ammonia water reach 2.82g/cm(3), 1.07MPam(1/2), and 18.2MPa, respectively.