Impact of hydroxyapatite (HaP) nano particle on the morphology, thickness, and adhesion strength of electrophoretic ZnO/HaP composite coated SS316L

Abstract

The present study explores how the hydroxyapatite (HAp) nanoparticles could influence the surface properties of the electrophoretic ZnO/HAp composite coating on stainless steel SS316L substrate. Various weight dispersion of HAp nanoparticles (1.0 g/l, and 1.5 g/l) and applied voltage of 40 V and 50 V were applied during the deposition of the composite coatings. The ZnO/HAp composite coatings were characterized using field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), contact angle, Vicker's hardness, surface profilometer, scratch tester, and atomic force microscopy (AFM) analyser. The composite coating with 1.5 g/l of HAp with an applied voltage of 40 V has exhibited a homogeneous distribution with higher coating thickness of 11.17 μm, and importantly, low porosity (< 0.94 %, which is <1 %). Crystal sizes increases from 19.2 to 28 nm when the applied voltage and weight dispersion of HAp is increased. FTIR analysis confirmed the higher deposition of polymeric groups in ZnO/HAp composite coatings irrespective to the weight dispersion and voltages. Furthermore, the higher dispersion of HAp has decreased the surface energy and roughness with optimum coating hardness. However, the better adhesion strength was achieved in comparison to the other composite coatings. The failures that occurred during the scratch test were further detailed in this study using the AFM and SEM.