2.4. Characterization Methods

The X-ray diffraction (XRD) analyses were performed using the Cu_Kα radiation (λ = 1.056 Å) of an XRD-6000 Shimadzu equipment (Duisburg, Germany). Data were collected between 10–80° diffraction angles.

SEM investigations were performed on HAp powder and HAp-based coatings, using the secondary electron beams (30 keV and 25 keV, respectively) of an Inspect S scanning electronic microscope from FEI (Thermo Fischer Scientific, Hillsboro, OR, USA). Before SEM analysis, all samples were capped with a thin conductive layer.

Fourier transform infrared spectroscopy (FT-IR) spectra of HAp powder and composite coatings, as well as infrared microscopy (IRM) maps of Hap-based coatings, were recorded on a Nicolet iN10 MX FT-IR microscope (Thermo Fischer Scientific, Waltham, MA, USA), equipped with an MCT liquid nitrogen cooled detector. The measurements, performed in the reflection mode, were collected in the 4000–600 cm⁻¹ wavenumber range, at 4 cm⁻¹ resolution. Multiple scans were co-added and converted to absorbance, in order to attain each IR spectrum, using in this respect the Ominc Picta software (Thermo Fischer Scientific Company, Waltham, MA, USA).