SYNTHESIS, CHARACTERIZATION, AND SINTERING BEHAVIOR OF CALCIUM HYDROXYAPATITE POWDERS WITH AVERAGE PARTICLE DIAMETERS OF 150 NM

摘要

Ceramic Oxide Nanopowders from Controlled Energetic Pyrolysis Technology (CONCEPT) is a continuous, large scale synthetic technique in which aerosolized precursors are rapidly combusted leading to the production of ceramic oxides as nano- or ultrafine powder. Through novel innovations, TAL Materials has developed methods whereby a wide variety of metal oxide ceramics can be synthesized from precursors with tailored elemental compositions in flammable carrier solvents. The work has recently been extended to the production of calcium phosphate powders, and the Ca/P phases which result are a function of the Ca/P ratio in the precursor. For example, when Ca/P=L5, pure α-Ca{sub}3(PO{sub}4){sub}2 (tricalcalcium phosphate or TCP) powders with ave. particle diameters of 150 nm are formed. At Ca/P=1.67, a mixture of calcium hydroxyapatite (HA) and a small amount of α-TCP results. The latter phase can be eliminated by increasing the Ca/P ratio to 1.7. Further increases in the Ca/P ratio result in powders which are mixtures of HA, CaCO{sub}3, and CaO. The average particle size of the HA is also 150 nm, and infrared spectroscopy shows [CO{sub}3]{sup}(2-) substitution into the HA lattice. A large excess of CO{sub}2 is a natural consequence of the combustion of organics in the precursor, and this broadens the region of HA formation into more Ca rich compositions as [CO{sub}3]{sup}(2-) occupies both [PO{sub}4]{sup}(3-) and [OH]{sup}(1-) sites. Preliminary sintering studies of the HA powder have resulted in ceramic bodies with near theoretical densities following procedures which include cold isostatic pressing of green bodies and sintering at 1100 °C for 30 min.