M. Evaristo

Ag:TiN nanocomposite thin films for bioelectrodes: The effect of annealing treatments on the electrical and mechanical behavior

Magnetron sputtered Ag:TiN thin films, with Ag contents ranging from 0 to ∼50 at. %, were subjected to a set of annealing treatments at four different temperatures (from 200 to 500 °C), aiming at studying the effect of Ag addition on their morphological and structural features, as well as on their electrical and mechanical properties. The increase of the annealing temperature revealed that significant morphological modifications were induced, mainly in the samples with higher Ag contents (represented by the sample with an Ag content of 36.3 at. %), which revealed extensive Ag segregation to the surface. The increase of the annealing temperature up to 500 °C, besides confirming the presence of metallic Ag in the coatings, also resulted in some major structural changes, promoting an increase in the coatings crystallinity and an extensive Ag grain growth phenomenon. Nevertheless, the resistivity values of all annealed samples were found to be only slightly higher when comparing to the as-deposited ones, whi...

The Influence of the Addition of Ti on the Mechanical Properties of W-S-Ti Coatings

In this work, W-S-Ti films were deposited by r.f. magnetron sputtering, using simultaneously WS2 and Ti targets. The atomic percentage of Ti in the coating was varied from 0 at.% up to 28 at.%. No significant variations in the S/W ratio with the increase of Ti content were observed. The increasing Ti contents in the films led to a gradual loss of crystallinity. Coatings with contents greater than ≈ 16 at.% only presents a broad peak characteristic of amorphous structures. Alloying the films with Ti led to significant improvements in the hardness (from 0.3 to 8.9 GPa). Also, the adhesive critical load continuously grew with the increase of the Ti content in the films. The wear coefficient of the films dropped more than one order of magnitude with the increase of Ti content whereas the friction coefficient was kept fairly constant with just a small increase in relation to single W-S film. In conclusion, to have a good tribological performance, the addition of Ti to the films should be balanced in order that the increase of the mechanical properties does not lead to severe loss of the self-lubricant properties.

Influence of carbon content on the nanotribology of W-S-C films

The objective of the present work is to evaluate the influence of carbon content on nanotribological response of reactively sputtered W-S-C thin film. Towards that purpose, W-S-C film containing varying amount of carbon was deposited on tool steel substrate using reactive sputtering. The nanohardness and lateral force microscopy of these films are determined using a nanoindenter and an atomic force microscope (AFM). The results show that the hardness and the pull off force are the maximum at intermediate carbon content. High carbon also appears detrimental for tribology at low load.