Inductively coupled radio frequency (RF) plasma spraying,powered by high-frequency oscillating electrical current,performed an important role in fine powder manufacture. Itwas used in the present study to prepare fine sphericalbioceramic powders of hydroxyapatite (HA) whose chemicalcomposition similar to those of natural bone. The as-sprayedpowders consisted of both micron-sized spherical particles andnano-sized particles. In addition to the spheroidization effect,rf plasma treatment led to the decomposition of HA intosecondary calcium phosphate phases including tri-calciumphosphate (TCP), tetra-calcium phosphate (TTCP) andcalcium oxide (CaO). The microstructure investigationshowed that the spheroidized particles were either fully denseor hollow structure with a shell. The reason for the formationof hollow spheres was contributed to the higher density of thesolidifying surface layer compared with the molten phaseduring solidification.
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