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

Michael Meindlhumer, Jakub Zalesak, Reinhard Pitonak, Juraj Todt, Bernhard Sartory, M. Burghammer, Andreas Stark, Norbert Schell, Rostislav Daniel, Julius Keckes, Mario Lessiak, A. Köpf, R. Weißenbacher, Jozef Keckes

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12 Citations (Scopus)

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 m 0.5 , 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.

Original languageEnglish
Pages (from-to)7986-7995
Number of pages10
JournalNanoscale
Volume11.2019
Issue number16
DOIs
Publication statusPublished - 28 Apr 2019

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