Eduardo Blando

Microhardness characterization of superlattices formed by reactive magnetron sputtering and ion beam assisted deposition

Abstract At present, the development of indentation techniques permits to perform measurements of hardness and other mechanical properties of a material with good accuracy, reproducibility and at a relatively low cost. Nevertheless, since the mechanical contact between indenter and material at low loads is very complex, it is difficult to attribute a hardness value to a film. Several models have been created to solve this problem and are currently in use. The use of particular deposition techniques permits the formation of multilayered coatings with a few nanometers thickness periodicity, which are namely superlattices and are characterized by extremely high hardness. The aim of this paper is to characterize multilayer coatings using the most important nano and microhardness models. The coatings were deposited by reactive magnetron sputtering and ion beam assisted deposition and consists of Cr/V and Ti/TiN layers. The layer periodicity, superlattices wavelengths and elemental characterization were studied by means of grazing angle X-ray diffraction and Rutherford backscattering spectroscopy. The microhardness tests were performed using a computer controlled dynamic load–unload process. The hardness values are either corrected for the indentation size effect or following Oliver–Pharr model. The results show an increase of the hardness values, confirming the development of a superlattice successfully formed by a magnetron sputtering system. The nano and microhardness models show differences in the hardness values obtained, probably due to the difficulty to estimate the real indented area.

Osseointegration of atmospheric plasma‐sprayed titanium implants: Influence of the native oxide layer

The aim of this study was to evaluate in vivo the influence of the native oxide layer on osseointegration and new bone formation on the surface of atmospheric plasma-sprayed porous titanium coatings. Porous titanium coatings were deposited on all implant surfaces, and half of the samples were subsequently submitted to oxide layer removal treatment. Samples were implanted onto the cortical bone of sheep (tibia) and evaluated at 30 and 60 days. Implants were removed en bloc and the attachment of bone to implants was examined by tensile pull-out test (osseointegration assessment), light microscopy, scanning electron microscopy (histological analysis), and instrumented hardness tests (mechanical properties of mature and newly formed bone tissue). Coatings submitted to oxide layer treatment presented higher osseointegration values at both healing periods and showed more mature and mineralized bone tissue when compared with nontreated coatings. Our findings showed that the use of acid-etching in association with atmospheric plasma spraying techniques improves osseointegration of titanium implants.