Amorphous, ultra-nano- and nano-crystalline tungsten-based coatings grown by Pulsed Laser Deposition: mechanical characterization by Surface Brillouin Spectroscopy
| Autor: | Matteo Passoni, David Dellasega, Andrea Pezzoli, E. Besozzi, Claudia Conti, Marco Beghi |
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| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
Materials science
XRD FOS: Physical sciences Physics::Optics Crystal growth 02 engineering and technology 01 natural sciences Tungsten coatings Pulsed laser deposition Crystal Condensed Matter::Materials Science Pulsed Laser Deposition 0103 physical sciences Tungsten - Tantalum lcsh:TA401-492 Mechanical Properties General Materials Science Composite material 010302 applied physics Condensed Matter - Materials Science Brillouin Spectroscopy Mechanical Engineering Materials Science (cond-mat.mtrl-sci) 021001 nanoscience & nanotechnology Grain size Nanocrystalline material Amorphous solid Crystallography Brillouin spectroscopy Mechanics of Materials Materials Science (all) lcsh:Materials of engineering and construction. Mechanics of materials Crystallite 0210 nano-technology |
| Zdroj: | Materials & Design, Vol 106, Iss, Pp 14-21 (2016) Materials & Design |
| Popis: | Pulsed Laser Deposition allows to obtain W and W-Ta alloy coatings with different nanostructures, monitored by X-ray diffraction. The correlation between such structures and the elastic properties is investigated for amorphous-like, ultra-nano- and nano-crystalline coatings obtained by tuning the gas pressure during deposition, annealing temperature and Ta concentration. The full elastic characterization is achieved by surface Brillouin spectroscopy, interpreted by isotropic and anisotropic film models. Amorphous like coatings are obtained with He pressures of tens of Pa. In comparison with bulk W, they have lower stiffness, by about 60\%, closely correlated to the mass density (lower by about 40\%). In the nanocrystalline regime the stiffness is more correlated to the average grain size, approaching the bulk values for increasing crystallite size. Vacuum annealing of amorphous like coatings leads to the nucleation of ultra-nano crystalline seeds, embedded in an amorphous matrix with intermediate values for mass density and stiffness. Here, the stiffness results from an interplay between the crystal size and the density. Alloying with Ta leads to properties which are consistent with the lever rule in the nanocrystalline regime, and deviate from it when the higher Ta concentration, interfering with crystal growth, induces an ultra-nano crystalline structure. Comment: The research leading to these results has also received funding from the European Research Council Consolidator Grant ENSURE (ERC-2014-CoG No. 647554) |
| Databáze: | OpenAIRE |
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