title: Radio frequency (rf) plasma spheroidized HA powders: powder characterization and spark plasma sintering behavior.
abstract: The present study describes the synthesis of spheroidized hydroxyapatite (HA) powders using a radio frequency (rf) inductively coupled plasma (ICP) torch. The spheroidized powders were consolidated through a spark plasma sintering (SPS) system. The microstructure and crystallographic phases in the synthesized powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Raman spectrometry. Results showed that the HA feedstock decomposed after rf plasma processing. Crystalline HA, alpha-tri-calcium phosphate (alpha-TCP), tetra-calcium phosphate (TTCP) and calcium oxide (CaO) were detected in the plasma-spheroidized powders. Raman spectra results indicated strong presence of amorphous calcium phosphate (ACP) in the spheroidized powders. The particle size distribution and specific surface area were influenced through the rf plasma working plate power levels. The sintering behavior of the rf plasma synthesized powders was analyzed through the SPS process and the results indicated that the spheroidized powders commence sintering at approximately 900 degrees C and through to 1150 degrees C. After sintering above 1100 degrees C for 3min, the relative densities of the SPS compacts reached 96% of the theoretical value. The SPS compacts were immersed in simulated body fluids (SBF) for different durations and the results confirmed their bioactivities.
authors.affiliation: School of Mechanical and Production Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
authors.forename: J L
authors.initials: JL
authors.lastname: Xu
authors.forename: K A
authors.initials: KA
authors.lastname: Khor
authors.forename: Y W
authors.initials: YW
authors.lastname: Gu
authors.forename: R
authors.initials: R
authors.lastname: Kumar
authors.forename: P
authors.initials: P
authors.lastname: Cheang
mesh_terms: D001672:Biocompatible Materials / Q000032:analysis / Q000737:chemistry / Q000528:radiation effects; D001826:Body Fluids / Q000737:chemistry*; D002130:Calcium Phosphates; D003460:Crystallization / Q000379:methods*; D017886:Durapatite / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D004548:Elasticity; D004574:Electromagnetic Fields; D006244:Hardness; D006358:Hot Temperature; D008422:Materials Testing; D008863:Microspheres; D010316:Particle Size; D044367:Phase Transition; D011208:Powders; D011846:Radio Waves; D013696:Temperature
chemical_list: D001672:Biocompatible Materials; D002130:Calcium Phosphates; D011208:Powders; C519480:amorphous calcium phosphate; D017886:Durapatite