Nano-mechanical properties and biotribological behaviors of nanosized HA/partially-stabilized zirconia composites

In this study, nanosized hydroxyapatite (HA) particles were synthesized by precipitation process using Ca(NO3)2·4H2O and (NH4)2 HPO4 at room temperature (25 °C) and atmospheric pressure. Pressureless sintering (PS) was used for comparing the sinterability of HA/yttria-partially-stabilized zirconia composites. The nanohardness and elastic modulus evaluations of all of HA/partially stabilized zirconia (PSZ) ceramics were obtained by nanoindentation tests with the corresponding load-displacement curves confoirming the characteristic properties of the sintered materials. It was found that HA/30% PSZ(w) composite showed the highest hardness values. A pin-slid-on-disc tribometer was run, as a comparative test method, to observe the tribological behaviors of these bioceramics against ultrahigh molecular weight polyethylene (UHMWPE) in human plasma lubrication. The experimental results demonstrated that the wear mechanism of UHMWPE was mainly fatigue wear. The lowest friction coefficient and wear rate were obtained for composite containing 30 wt.% of nanosized PSZ(Y). The analysis of nitrogen element indicated that the serous protein deposited on the friction and wear surfaces. As a result, the lower wear rate of UHMWPE was obtained in human plasma lubrication.