The effect of ZnO nanoparticles on nanomechanical behavior of Hydroxyapatite electrodeposited on NiTi biomedical alloy

Abstract

This paper aims at surface characterization, chemical composition, and mechanical properties of Hydroxyapa-tite/ZnO (HA/ZnO) nanocomposite coatings on NiTi biomedical alloy. Morphological observations by FESEM and AFM techniques showed that ZnO NPs were responsible for a uniform, porous HA matrix. XRD analysis proved the pure HA phase synthesis in the presence of ZnO NPs; without them, there were other secondary CaP phases. XPS chemical state investigations firmly confirmed the presence of ZnO NPs by showing peaks at 531.05 eV (O Zn bond) and 1021.82 eV (Zn O bond). Nano-hardness test highlighted a significant enhancement in hardness of composite coating (0.37 GPa) compared to pure HA coating (0.19 GPa). The notable point was that HA/ZnO nanocomposite exhibited more plasticity than HA simple coating. This is beneficial as it provides a comfortable spot for cellular activities. Last but not least, the nano-scratch analysis revealed a great effect of ZnO inclusion on reducing friction coefficient by around 40%. The critical load was also much higher for HA/ZnO composite coating (91.4 mN) than HA coating (58.5 mN). Owing to higher plasticity and lower friction coeffi-cient, HA/ZnO composite managed to ease the movement of the indenter tip on its surface, thereby suffering less shear stress.