Spin-coating synthesis and characterization of Zn-doped hydroxyapatite/polylactic acid composite coatings

Zn-doped hydroxyapatite/polylactic acid (HA/PLA) composite coatings fabricated by spin-coating technique have rarely been studied by other researchers in recent years. In this study, Zn-doped hydroxyapatite (Zn-doped HA) powder were synthesized by chemical precipitation method, and then Zn-doped hydroxyapatite/polylactic acid (Zn-doped HA/PLA) composite coatings were coated on stainless steel substrates using a spin-coating technique for the first time. The effects of heat treatment in air at 600   °C on the composition and morphology of Zn-doped HA/PLA composite coatings with a series of molar ratios of zinc (0   mol%, 5   mol%, 10   mol%, 15   mol% and 20   mol%) were studied. The obtained samples were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The results showed that Zn 2   + ions had replaced the partial Ca 2   + ions and were doped into hydroxyapatite lattice successfully. The synthetic hydroxyapatite nanoparticles showed rod-like morphology, whereas the substitution of the Zn ions restrained the growth of Zn-doped HA crystal and decreased its size. The surface morphology of Zn-doped HA/PLA composite coatings after sintering at 600   °C for 1   h exhibited a uniform, porous structure with a thickness of 60   μm or so. The introduction of PLA in composite coatings could keep metal substrates from catalyzing the decomposition of HA caused by high temperature heat treatment.