A Molecular‐Scale Understanding of Misorientation Toughening in Corals and Seashells
Abstract
Biominerals are organic–mineral composites formed by living organisms. They are the hardest and toughest tissues in those organisms, are often polycrystalline, and their mesostructure (which includes nano‐ and microscale crystallite size, shape, arrangement, and orientation) can vary dramatically. Marine biominerals may be aragonite, vaterite, or calcite, all calcium carbonate (CaCO3) polymorphs, differing in crystal structure. Unexpectedly, diverse CaCO3 biominerals such as coral skeletons and nacre share a similar characteristic: Adjacent crystals are slightly misoriented. This observation is documented quantitatively at the micro‐ and nanoscales, using polarization‐dependent imaging contrast mapping (PIC mapping), and the slight misorientations are consistently between 1° and 40°. Nanoindentation shows that both polycrystalline biominerals and abiotic synthetic spherulites are tougher than single‐crystalline geologic aragonite. Molecular dynamics (MD) simulations of bicrystals at the molecular scale reveal that aragonite, vaterite, and calcite exhibit toughness maxima when the bicrystals are misoriented by 10°, 20°, and 30°, respectively, demonstrating that slight misorientation alone can increase fracture toughness. Slight‐misorientation‐toughening can be harnessed for synthesis of bioinspired materials that only require one material, are not limited to specific top‐down architecture, and are easily achieved by self‐assembly of organic molecules (e.g., aspirin, chocolate), polymers, metals, and ceramics well beyond biominerals.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Apr 25, 2023
- Source ID
- 10.1002/adma.202300373
Entities
People
- Alexandra Tits
- Andreas Scholl
- Andrew J Lew
- Astrid Cantamessa
- Cayla A. Stifler
- Connor A. Schmidt
- Davide Ruffoni
- Laura Müller
- Markus J. Buehler
- Philippe Compère
- Pupa Gilbert
- Yann Delaunois
Organizations
- Army Research Office
- Lawrence Berkeley National Laboratory
- Massachusetts Institute of Technology
- National Science Foundation
- Office of Naval Research
- University of Liège
- University of Wisconsin–Madison