Abstract No.:
5299

 Scheduled at:
Wednesday, June 07, 2017, Hall 14 3:00 PM
Medical Industry II


 Title:
The influence of stand-off distance on phase composition of in-flight particles and hydroxyapatite coatings

 Authors:
Xiaomei Liu* / College of Materials Science and Engineering, P.R. China
Yiming Wang / Beijing University of Technology , China
Zheng Zhou/ Beijing University of Technology , China
Guohong Wang/ Beijing University of Technology , China
Zhen Tan/ Beijing University of Technology , China
Dingyong He/ Beijing University of Technology, China

 Abstract:
Phase composition of in-flight particles significantly affects the biological and mechanical properties of final hydroxyapatite (HA) coating. It is known that high crystallinity HA coatings with (002) texture was obtained by micro-plasma spraying (MPS). Therefore, in the present study, HA coatings were deposited on Ti-6Al-4V by MPS at different stand-off distances (SOD) (60-110 mm). The corresponding in-flight particles were collected by liquid nitrogen. Morphologies of initial powder and in-flight particles were characterized by using scanning electron microscopy (SEM). Particle size distribution and melt fraction of the in-flight particles were evaluated. The phase composition along cross section of single in-flight particle was analyzed by micro-Raman spectrometer (MRS). X-ray diffraction (XRD) was employed to analyze the phase composition of collected in-flight particles and HA coatings. The results indicated that the surface of in-flight particles became smoother and denser due to the melt of outer layer during MPS. Smaller particles were obtained at longer SOD. Most of the observed in-flight particles were in melt state at all investigated SOD. However, with increasing SOD, the phase decomposition and amorphous calcium phase (ACP) within melt region of in-flight particles were increased. The decomposition phases mainly included dehydroxyapatite and tricalcium phosphate (TCP). This was consistent with the phase composition observed in HA coating at the same experimental condition. Moreover, some of the in-flight particles exhibited un-directional solidification feature at SOD above 110 mm, due to the temperature decrease along with increasing SOD. This was leading to the decreasing (002) texture in HA coating at long SOD.
Keywords: hydroxyapatite; in-flight particle; micro-plasma spraying


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