Growth, characterization and functional properties of thin films on metal and ceramic substrates

Functional properties are mechanical, physical and chemical characteristics of the material depending both on the bulk of the material and on functional surface films. In this work, an analytical method was developed for studying the growth and characterization of thin layers (used to improve the functional properties of materials such as ceramics, brass and steel), combining electrochemical and tribological in-situ techniques with the X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy (XAES) (ex-situ). The data quality in the XPS analysis was controlled and evaluated by periodic calibrations according to ISO 15472:2014 protocol and by using reference materials for an accurate qualitative and quantitative analysis. The first part of this thesis is focussed on the study of the corrosion behaviour of the brass CuZn37 and the DIN 1.4456 Ni-free stainless-steel alloys exposed to three model saliva formulations, Darvell, Carter-Brugirard and SALMO, differing for the organic compounds content. The corrosion behaviour of the CuZn37 and of the Ni-free stainless steel in contact with the artificial saliva was evaluated with electrochemical studies (OCP and LPR) at different exposure times (1h, 3h and 16h). In the second part of this thesis, the focus is on the lubrication mechanism of [EMIM]EtSO4 and a mixture of [EMIM]EtSO4 + 2 wt % of an equimolar ratio of oleic acid and [EMIM] oleate for the sliding of a Si3N4 tribopair. The influence of the water uptake during the experiment carried out with a relative humidity (RH) of 43.5-55% and the effect of the additive are evaluated. This work confirms that the analytical approach based on combination of in-situ techniques and ex-situ techniques following a careful calibration and the analysis of reference materials allow the rationalization of the results and the understanding of the mechanisms of the role played by the surface film composition both in corrosion and in tribology.

Functional properties are mechanical, physical and chemical characteristics of the material depending both on the bulk of the material and on functional surface films. In this work, an analytical method was developed for studying the growth and characterization of thin layers (used to improve the functional properties of materials such as ceramics, brass and steel), combining electrochemical and tribological in-situ techniques with the X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy (XAES) (ex-situ). The data quality in the XPS analysis was controlled and evaluated by periodic calibrations according to ISO 15472:2014 and by using reference materials for an accurate qualitative and quantitative analysis. The first part of this thesis is focussed on the study of the corrosion behaviour of the brass CuZn37 and the DIN 1.4456 Ni-free stainless-steel alloys exposed to three model saliva formulations, Darvell, Carter-Brugirard and SALMO, differing for the organic compounds content. The corrosion behaviour of the CuZn37 and of the Ni-free stainless steel in contact with the artificial saliva was evaluated with electrochemical studies (OCP and LPR) at different exposure times (1h, 3h and 16h). In the second part of this thesis, the focus is on the lubrication mechanism of [EMIM]EtSO4 and a mixture of [EMIM]EtSO4 + 2 wt % of an equimolar ratio of oleic acid and [EMIM] oleate for the sliding of a Si3N4 tribopair. The influence of the water uptake during the experiment carried out with a relative humidity (RH) of 43.5-55% and the effect of the additive are evaluated. This work confirms that the analytical approach based on combination of in-situ techniques and ex-situ techniques following a careful calibration and the analysis of reference materials allow the rationalization of the results and the understanding of the mechanisms of the role played by the surface film composition both in corrosion and in tribology.