Strategies for simultaneous strengthening and toughening via nanoscopic intracrystalline defects in a biogenic ceramic

ZF Deng and HS Chen and T Yang and Z Jia and JC Weaver and PD Shevchenko and F De Carlo and R Mirzaeifar and L Li, NATURE COMMUNICATIONS, 11, 5678 (2020).

DOI: 10.1038/s41467-020-19416-2

While many organisms synthesize robust skeletal composites consisting of spatially discrete organic and mineral (ceramic) phases, the intrinsic mechanical properties of the mineral phases are poorly understood. Using the shell of the marine bivalve Atrina rigida as a model system, and through a combination of multiscale structural and mechanical characterization in conjunction with theoretical and computational modeling, we uncover the underlying mechanical roles of a ubiquitous structural motif in biogenic calcite, their nanoscopic intracrystalline defects. These nanoscopic defects not only suppress the soft yielding of pure calcite through the classical precipitation strengthening mechanism, but also enhance energy dissipation through controlled nano- and micro-fracture, where the defects' size, geometry, orientation, and distribution facilitate and guide crack initialization and propagation. These nano- and micro-scale cracks are further confined by larger scale intercrystalline organic interfaces, enabling further improved damage tolerance. Biominerals are nanocomposites that often incorporate nanoscopic defects such as organic inclusions within the mineral matrix. Here, the authors report on an experimental and computational study into the effects of intracrystalline defects on the intrinsic mechanical behaviour of biominerals.

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