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Structure and mechanical properties of TiAlN-WNI(x) thin films
Rhein Westfal TH Aachen.
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-2837-3656
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2011 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 205, no 20, 4821-4827 p.Article in journal (Refereed) Published
Abstract [en]

A combinatorial method was employed to grow TiAlN-WNx films by DC sputtering as well as by High Power Pulsed Magnetron Sputtering (HPPMS) where the W concentration was varied between 10-52 at.% and 7-54 at.%, respectively. Experiments were paired with ab initio calculations to investigate the correlation between composition, structure, and mechanical properties. During all depositions the time averaged power was kept constant. As the W concentration was increased, the lattice parameter of cubic TiAlN-WNx films first increased and then decreased for W concentrations above approximate to 29 at.% (DCMS) and approximate to 27 at.% (HPPMS) as the N concentration decreased. Calculations helped to attribute the increase to the substitution of Ti and Al by W and the decrease to the presence of N vacancies. Youngs modulus and hardness were around 385-400 GPa and 29-31 GPa for DCMS and 430-480 GPa and 34-38 GPa for HPPMS, respectively, showing no significant trend as the W concentration was increased, whereas calculations showed a continuous decrease in Youngs modulus from 440 to 325 GPa as the W concentration was increased from 0 to 37.5 at.%. The presence of N vacancies was shown to increase the calculated Youngs modulus. Hence, the relatively constant values measured may be understood based on N vacancy formation as the W concentration was increased. HPPMS-deposited films exceed DCMS films in Youngs modulus and hardness, which may be a consequence of the larger degree of ionization in the HPPMS plasma. It is reasonable to assume that especially the ionized film forming species may contribute towards film densification and N vacancy formation.

Place, publisher, year, edition, pages
Elsevier Science B.V., Amsterdam. , 2011. Vol. 205, no 20, 4821-4827 p.
Keyword [en]
TiAl-WNx; HPPMS/HiPIMS; Combinatorial sputtering; Ab initio calculation; Structure; Elastic properties
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-69794DOI: 10.1016/j.surfcoat.2011.04.066ISI: 000292361400012OAI: oai:DiVA.org:liu-69794DiVA: diva2:433577
Available from: 2011-08-10 Created: 2011-08-08 Last updated: 2017-12-08
In thesis
1. Transition Metal Nitrides: Alloy Design and Surface Transport Properties using Ab-initio and Classical Computational Methods
Open this publication in new window or tab >>Transition Metal Nitrides: Alloy Design and Surface Transport Properties using Ab-initio and Classical Computational Methods
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Enhanced toughness in brittle ceramic materials, such as transition metal nitrides (TMN), is achieved by optimizing the occupancy of shear-sensitive metallic electronic-states. This is the major result of my theoretical research, aimed to solve an inherent long-standing problem for hard ceramic protective coatings: brittleness. High hardness, in combination with high toughness, is thus one of the most desired mechanical/physical properties in modern coatings. A significant part of this PhD Thesis is dedicated to the density functional theory (DFT) calculations carried out to understand the electronic origins of ductility, and to predict novel TMN alloys with optimal hardness/toughness ratios. Importantly, one of the TMN alloys identified in my theoretical work has subsequently been synthesized in the laboratory and exhibits the predicted properties.

The second part of this Thesis concerns molecular dynamics (MD) simulations of Ti, N, and TiNx adspecies diffusion on TiN surfaces, chosen as a model material, to provide unprecedented detail of critical atomic-scale transport processes, which dictate the growth modes of TMN thin films. Even the most advanced experimental techniques cannot provide sufficient information on the kinetics and dynamics of picosecond atomistic processes, which affect thin films nucleation and growth. Information on these phenomena would allow experimentalists to better understand the role of deposition conditions and fine tune thin films growth modes, to tailor coatings properties to the requirements of different applications. The MD simulations discussed in the second part of this PhD Thesis, predict that Ti adatoms and TiN2 admolecules are the most mobile species on TiN(001) terraces. Moreover, these adspecies are rapidly incorporated at island descending steps, and primarily contribute to layer-by-layer growth. In contrast, TiN3 tetramers are found to be essentially stationary on both TiN(001) terraces and islands, and thus constitute the critical nuclei for three-dimensional growth.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. 75 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1513
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-91379 (URN)978-91-7519-638-1 (ISBN)
Public defence
2013-05-23, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
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Available from: 2013-04-23 Created: 2013-04-23 Last updated: 2016-08-31Bibliographically approved

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Sangiovanni, DavideChirita, ValeriuHultman, Lars

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