Journal
SCRIPTA MATERIALIA
Volume 194, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.scriptamat.2020.113684
Keywords
Two-photon polymerization direct laser writing; Pyrolytic carbon; Fracture toughness; Pillar splitting; Humidity
Categories
Funding
- European Commission, European project Oyster [760827]
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This study introduces a new method to measure the mechanical properties of 3D-printed nano-ceramics and reveals that nanometer-sized surface cavities can cause embrittlement and promote crack propagation. It demonstrates that reliability and durability of micro- and nano-architected ceramic metamaterials and devices require toughening design approaches focusing on size-dependent surface effects.
3D-printed nano-architected ceramic metamaterials currently emerge as a class of lightweight materials with exceptional strength and stiffness. However, their application is hampered by the lack of knowledge on their mechanical reliability. Characteristics like the fracture strength and their dependency on environmental conditions are unknown. We herein present and discuss a nano-indentation pillar splitting method to measure fracture toughness, elastic modulus, and hardness of 3D-printed nano-ceramics. We show that two photon polymerization-derived pyrolytic carbon achieves improved fracture toughness over macroscopic forms of vitreous carbon, with values up to 3.1 MPam(0.5). However, experiments at different humidity levels reveal that only few, nanometer-sized, surface cavities can cause embrittlement from liquid diffusion, which promotes earlier crack propagation. While comparable effects are less relevant in macro-size ceramics, this study demonstrates that reliability and durability of micro- and nano-architected ceramic metamaterials and devices requires toughening design approaches that focus on size-dependent surface effects. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd.
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