Materials and methods PPD technique was used to deposit ZTA coatings; this technique is able to maintain the stoichiometry of the starting target. In this study we started from a cylindrical ZTA target (30 mm diameter × 5 mm thickness, 75% alumina / 25% zirconia) and followed the procedure described by Bianchi et al . Characterization of morphology, micro-structure and chemistry of deposited coatings was performed by Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS) and Atomic Force Microscope (AFM). Coating-substrate interface quality were investigated by micro-scratch tests. Measurement of the contact angle between a drop of 1 ml of ultrapure water and the surface of the sample was performed to estimate the degree of wetting. A ZTA-coated stainless steel ball (AISI 420, 3 mm radius) was coupled against medical grade UHMWPE to evaluate the friction of the proposed coupling in preliminary ball-on-disk tribological tests.
Results Coatings up to several microns thick have been deposited by PPD. Deposited ZTA films exhibited a smooth nanostructured surface.
Mechanical tests showed a well-adherent films were deposited. In particular, scratch tests assessed a good interface adhesion: first formation of cracking in the coating during testing was reported at about 0.8 N
Hydrophobic behavior of the coating was revealed by contact angles (average contact angle 116° ± 2°), probably due to the nano-roughness of the coating itself.
Good average friction coefficient ranging from 0.12 to 0.15 was showed by preliminary tribological tests carried out in deionized water after up to 10000 m tracks.
Conclusions The preliminary results of a novel approach aiming to drastically improve the performance of prosthetic couplings by introducing hard ceramic coating was presented. Showed results suggested the feasibility of pursuing this approach of realizing ZTA coatings by means of PPD technique. Further analyses on mechanical properties, nanoroughness and tribology are ongoing. Well-adherent ZTA films deposited directly on the prosthetic components surface would then allow a drastic improvement of the actual prosthetic behaviour.
|Journal||Bone and Joint Journal|
|Publication status||Published - May 25 2016|