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Biomimetic hard and tough nanoceramic Ti–Al–N film with self-assembled six-level hierarchy

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Abstract

Nature uses self-assembly of a fairly limited selection of components to build hard and tough protective tissues like nacre and enamel. The resulting hierarchical micro/nanostructures provide decisive toughening mechanisms while preserving strength. However, to mimic microstructural and mechanical characteristics of natural materials in application-relevant synthetic nanostructures has proven to be difficult. Here, we demonstrate a biomimetic synthesis strategy, based on chemical vapour deposition technology, employed to fabricate a protective high-temperature resistant nanostructured ceramic TiAlN thin film with six levels of hierarchy. By using just two variants of gaseous precursors and through bottom-up self-assembly, an irregularly arranged hard and tough multilayer stack was formed, consisting of hard sublayers with herringbone micrograins, separated by tough interlayers with spherical nanograins, respectively composed of lamellar nanostructures of alternating coherent/incoherent, hard/tough, single-/poly-crystalline platelets. Micro- and nanomechanical testing, performed in situ in scanning and transmission electron microscopes, manifests intrinsic toughening mechanisms mediated by five types of interfaces resulting in intergranular, transgranular and cleavage fracture modes with zigzag-like crack patterns at multiple length-scales. The hierarchical 2.7 μm thick film self-assembled during ∼15 minutes of deposition time shows hardness, fracture stress and toughness of ∼31 GPa, ∼7.9 GPa and ∼4.7 MPa m0.5, respectively, as well as phase/microstructural thermal stability up to ∼950/900 °C. The film's microstructural and mechanical characteristics represent a milestone in the production of protective and wear-resistant thin films.

Graphical abstract: Biomimetic hard and tough nanoceramic Ti–Al–N film with self-assembled six-level hierarchy

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Publication details

The article was received on 21 Dec 2018, accepted on 20 Mar 2019 and first published on 10 Apr 2019


Article type: Paper
DOI: 10.1039/C8NR10339A
Citation: Nanoscale, 2019, Advance Article
  • Open access: Creative Commons BY license
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    Biomimetic hard and tough nanoceramic Ti–Al–N film with self-assembled six-level hierarchy

    M. Meindlhumer, J. Zalesak, R. Pitonak, J. Todt, B. Sartory, M. Burghammer, A. Stark, N. Schell, R. Daniel, J. F. Keckes, M. Lessiak, A. Köpf, R. Weißenbacher and J. Keckes, Nanoscale, 2019, Advance Article , DOI: 10.1039/C8NR10339A

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