An X’PertPro MPD PANalytical X-ray diffractometer and grazing incidence X-ray diffraction technique (GIXD) with CuKα radiation were used to determine the structural properties of the substrate and coat-forming material. The GIXD patterns were measured at a constant incidence angle of 0.3° at room temperature. A confocal Raman spectrometer WITec alpha 300 R equipped with a laser (λ = 532 nm, P = 40 mW) and a high sensitivity back-illuminated Newton-CCD camera was applied to local structural investigation of the coat-forming materials. As a result, Raman imaging was carried out in a 1600 µm2 area, taking into account 25,600 pixels (=spectra) and an integration time of 60 ms per spectrum. All the spectra were collected at room temperature using Olympus objective (100×/0.9 NA), a lateral resolution of 3 cm−1, precision of 1 cm−1, and a 120–4000 cm−1 range. The data in post-processing analysis were subjected to cosmic ray removal and baseline correction using WITec Project Four Plus (version 4.1, WITec Wissenschaftliche Instrumente und Technologie GmbH, Ulm, Germany). A Lorentz–Gauss function is applied to band fitting using the Grams (version 9.2, Thermo Fisher Scientific, Waltham, MA, USA) software package.
Before and after the deposition, the materials’ morphology was visualized using a JEOL JSM-6480 and a TESCAN Mira 3 LMU scanning electron microscope (SEM). Samples for the NiTi/coating cross-section SEM observations were embedded in graphite resin and polished with 2000-grit SiC paper, 1-µm diamond suspension, and finally, 0.1-μm colloidal silica suspension, to achieve a mirror finish. Observations were carried out for samples covered with a 5 nm Cr layer using Quorum Q150T ES equipment. The deformation ability of the HAp coating was observed using a scanning electron microscope during the constant clamp deformation. The implant was first immersed in liquid nitrogen to induce the martensitic transformation and, next, subjected to deformation. After the implant returned to the initial shape at room temperature, the procedure was repeated. Measurements of water contact angle were taken with an OCA 15EC goniometer, with accuracy reaching ±0.01°, by the sitting drop method. Ten images of water drop having a volume of ca 5 µL, placed on the examined surface, were recorded for 10 s. The average contact angle (CA) values were calculated based on the obtained images. The contact angle final value was assumed to be the average of three measurements taken in different parts of the examined surface.
Before and after the deposition, the materials’ morphology was visualized using a JEOL JSM-6480 and a TESCAN Mira 3 LMU scanning electron microscope (SEM). Samples for the NiTi/coating cross-section SEM observations were embedded in graphite resin and polished with 2000-grit SiC paper, 1-µm diamond suspension, and finally, 0.1-μm colloidal silica suspension, to achieve a mirror finish. Observations were carried out for samples covered with a 5 nm Cr layer using Quorum Q150T ES equipment. The deformation ability of the HAp coating was observed using a scanning electron microscope during the constant clamp deformation. The implant was first immersed in liquid nitrogen to induce the martensitic transformation and, next, subjected to deformation. After the implant returned to the initial shape at room temperature, the procedure was repeated. Measurements of water contact angle were taken with an OCA 15EC goniometer, with accuracy reaching ±0.01°, by the sitting drop method. Ten images of water drop having a volume of ca 5 µL, placed on the examined surface, were recorded for 10 s. The average contact angle (CA) values were calculated based on the obtained images. The contact angle final value was assumed to be the average of three measurements taken in different parts of the examined surface.
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