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Keynote Lecture

Are nanostructured transition metal aluminium nitrides predictable? - Lessons learned from studying phase formation, elastic properties and fracture toughness

Wednesday (26.09.2018)
10:45 - 11:15 S1/03 - 23
Part of:

The combination of modern electronic structure calculations with the highly efficient combinatorial thin film composition-spread method is accepted to constitute an effective tool for knowledge-based materials design [1] including metastable thin film materials [2]. Property predictions as well as experimental synthesis and characterization reports are compared for transition metal aluminum nitride coatings, of which TiAlN is commercially available since the late 1980’s. The wide range of critical Al solubilities for metastable cubic Ti1−xAlxN from xmax = 0.4 to 0.9 reported in literature and the sobering disagreement thereof with DFT predictions can at least in part be rationalized based on crystallite size-dependent metastable phase formation [3]. Comparing the reported elastic modulus (range) for Cr0.8Al0.2N coatings, another commercially successful coating material, to predictions is an equally sobering experience: the measured Young’s modulus ranges from approximately 250 to 420GPa. This Young’s modulus spread of 170GPa is consistent with 60% of the upper Young’s modulus bound. And will at least in part be rationalized by considering the temperature and stress dependence of the Young’s modulus [4]. Furthermore, the impact of stress on the critical solubility of Al in VAlN is discussed [5,6]. Finally, it is demonstrated that ab initio predictions of the Young’s modulus are useful for predicting fracture toughness trends of transition metal aluminum nitride and oxynitride coatings [7].

[1] Gebhardt et al, Thin Solid Films 520, 5491-5499 (2012)

[2] Chang et al., Science and Technology of Advanced Materials 17 (1) (2016) 210-219

[3] Hans et al., Scientific Reports 7 (2017) 16096

[4] Music et al., Journal of Applied Physics 121 (2017) 215108-1

[5] Greczynski et al., Journal of Applied Physics 122 (2017) 025304-1

[6] Greczynski et al., Scientific Reports 7 (2017) 17544

[7] Gibson et al., Materials Research Letters 6 (2) (2018) 142-151


Prof. Jochen M. Schneider
RWTH Aachen University