Preliminary study on copper-doped hydroxyapatite coatings obtained using solution precursor plasma spray process

In the present study, copper-doped hydroxyapatite (Cu-HA) coating was deposited using solution precursor plasma spray process. Single torch scan experiments using different scan speeds, solution flow rates and spray distances were used as preliminary tests to screen the spray parameters suitable for the deposition of SPPS Cu-HA coatings. Further optimization of spraying parameters of coatings was made by varying the spraying distances from 50 mm to 70 mm with 10 mm increment. X-ray diffraction (XRD) analysis shows that hydroxyapatite is the dominant phase in the coating with a fraction of tricalcium phosphate (TCP's) and some traces of CaO and CuO. Fourier transform infrared spectroscopy (FTIR) results show increasing dehydroxylation of HA with the spray distance. Scanning electron (SEM) micrographs show agglomerated spherical particles, melted particles and pores at the surface. The cross-sections of the coatings show that relatively dense microstructure with cone-tip defects. Increasing the spraying distance results in the increase of porosity of coatings. The final optimized parameters enables obtaining the coating having about 81% HA phase, about 85% crystallinity, and dense microstructure with fine spherical particles.