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Structural and tribological characterization of tungsten nitride coatings at el...
Polcar, T.; Parreira, N. M. G.; Cavaleiro, A.Transition metal nitrides exhibit excellent mechanical properties (hardness and Young's modulus), high melting point, good chemical stability and high electrical conductivity. However, tungsten nitrides still stand aside of the main attention. In our previous study, tungsten nitride coatings with different nitrogen content showed excellent wear resistance at room temperature. Nevertheless, many engineering appl...
Influence of air oxidation on the properties of decorative NbOxNy coatings prep...
Chappé, J. M.; Carvalho, P.; Lanceros-Mendez, S.; Vasilevskiy, M. I.; Vaz, F.; Machado, A. V.; Fenker, M.; Kappl, H.; Parreira, N. M. G.; Cavaleiro, A.In this work the oxidation resistance of DC reactive sputtered niobium oxynitrides and its influence on the properties of the films are studied. The depositions have been carried out by DC magnetron sputtering with a reactive gas pulsing process. The nitrogen flow was kept constant and the oxygen flow was pulsed. Pulse durations of 10 s produced multilayer coatings with a period of [lambda] = 10 nm. Three sets ...
Structural and mechanical properties of Ti–Si–C–ON for biomedical applications
Guimarães, Freddy; Oliveira, Cristina; Sequeiros, Elsa; Torres, Marta; Susano, M.; Henriques, Mariana; Oliveira, Rosário; Escobar Galindo, R.Ti–Si–C–ON films were deposited by DC reactive magnetron sputtering using different partial pressure of oxygen (pO2) and nitrogen (pN2) ratio. Compositional analysis revealed the existence of two different growth zones for the films; one zone deposited under low pO2/pN2 and another zone deposited under high pO2/pN2. The films produced under low pO2/pN2 were deposited at a lower rate and presented a fcc structur...
Tungsten oxide with different oxygen contents: Sliding properties
Polcar, T.; Parreira, N. M. G.; Cavaleiro, A.In this study, tungsten oxide coatings with 13 and 75 at% of oxygen were prepared by DC reactive magnetron sputtering from a pure W target in an Ar+O2 atmosphere. The coating hardness (H) decreased with increasing oxygen content from 25 to 7.7 GPa. The values of H/E ratio were 0.08 and 0.07 for W87O13 and W25O75, respectively. ; http://www.sciencedirect.com/science/article/B6TW4-4NG3T6T-3/1/f9d8350fca3dc06d1...
Thermal stability of reactive sputtered tungsten oxide coatings
Parreira, N. M. G.; Polcar, T.; Cavaleiro, A.The thermal stability of different W-O coatings, W100, W90O10, W54O46, W30O70 and W25O75, were studied by in-situ X-ray diffraction at elevated temperatures up to 900 °C. The coatings were deposited by DC reactive magnetron sputtering from a pure tungsten target in an Ar + O2 atmosphere onto Fecralloy alloy. The evolution of the structure of the coatings was studied in both protective and oxidant atmospheres. T...
The influence of structure changes in the properties of TiCxOy decorative thin ...
Fernandes, A. C.; Vaz, F.; Cunha, L.; Parreira, N. M. G.; Cavaleiro, A.; Goudeau, Ph.; Bourhis, E. Le; Rivière, J. P.; Munteanu, D.; Borcea, B.The main purpose of this work consists in the preparation of titanium oxycarbide, TiCxOy, thin films, in which the presence of oxygen changed the film properties between those of titanium carbide and those of titanium oxide. Varying the oxide/carbide ratio allowed to tune the structure of the films between titanium oxide and carbide and consequently electronic, mechanical and optical properties of the films. Th...
Tribological characterization of tungsten nitride coatings deposited by reactiv...
Polcar, T.; Parreira, N. M. G.; Cavaleiro, A.The structure, hardness, friction and wear of tungsten nitrides prepared by d.c. reactive magnetron sputtering were investigated. The coatings were deposited with different nitrogen to argon ratios; the total pressure was kept constant. The tribological tests were performed on a pin-on-disc tribometer in terrestrial atmosphere with 100Cr6 steel, Al2O3 and Si3N4 balls as sliding counter-bodies. The wear tracks, ...
Influence of the O/C ratio in the behaviour of TiCxOy thin films
Fernandes, A. C.; Vaz, F.; Rebouta, L.; Pinto, A.; Alves, E.; Parreira, N. M. G.; Goudeau, Ph.; Bourhis, E. Le; Rivière, J. P.The main purpose of this work consists in the preparation of single layered titanium oxycarbide, TiCxOy, thin films. The obtained results show that the evolution of the different elements concentration with the oxygen flow can be divided into 3 different regimes -- i) carbide, zone I, ii) transition, zone T, and iii) an oxide one, zone II. Structure characterization results showed that the films crystallize in ...
Property change in multifunctional TiCxOy thin films: Effect of the O/Ti ratio
Fernandes, A. C.; Carvalho, P.; Vaz, F.; Lanceros-Méndez, S.; Machado, A. V.; Parreira, N. M. G.; Pierson, J. F.; Martin, N.TiCxOy films with various O/Ti ratios have been deposited by DC magnetron sputtering, using C pieces incrusted in a Ti target erosion area. Composition analysis revealed the existence of three different growth regimes: (i) zone I, corresponding to films with metallic-like appearance, and atomic ratios O/Ti below one; (ii) zone II, with films revealing interference-like colours, and atomic ratios O/Ti higher tha...
Synthesis, structural and mechanical characterization of sputtered tungsten oxi...
Parreira, N. M. G.; Carvalho, N. J. M.; Cavaleiro, A.Tungsten oxide coatings were deposited without substrate bias by DC reactive magnetron sputtering of a tungsten target using oxygen as reactive gas. By tuning the partial pressure of oxygen (pO2/pAr) between 0 and 4, the oxygen content of the films was changed from 0 to 75 at.%. The structure of the films (investigated by X-ray diffraction) depends on their oxygen content. For low oxygen contents, the [alpha]-W...
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