Crystallographic relationships in the crossed lamellar microstructure of the shell of the gastropod Conus marmoreus
authors Rodriguez-Navarro, AB; Checa, A; Willinger, MG; Bolmaro, R; Bonarski, J
nationality International
author keywords Biomineralization; Aragonite; Epitaxy; Twinning; Mollusk
abstract The crossed lamellar microstructure of mollusk shells shows a very complex hierarchical architecture constituted of long rod-shaped aragonite crystals stacked parallel to each other inside each first order lamella, which are almost perpendicular to the ones contained in parallel neighboring lamellae. To better understand the construction and properties of the crossed lamellar microstructure we have performed a detailed study to determine the crystallographic characteristics and their evolution during shell growth using scanning electron microscopy, transmission electron microscopy and X-ray diffraction texture analysis. The arrangement of crystals is rationalized by a set of twin law relationships between aragonite crystals. Specifically, the aragonite rods, or third order lamellae within each first order lamella, internally consist of polysynthetic twins bounded by {1 1 0} mirror planes. In turn, the polysynthetically twinned aragonite crystals also show a constant crystallographic orientation with respect to aragonite crystals in adjacent first order lamellae. It can be seen as another twin law in which crystals from adjacent lamellae are bounded by (1 1 0) planes but with their c-axes rotated within this plane by 30 degrees. Thus there are two sets of twin laws that relate crystal units at lower (third order lamellae) and higher (first order lamellae) length scales. These hierarchical relationships play a crucial role in the construction, organization and properties of this complex microstructure. The later orientational relationships have never been described in geological aragonite and are only found in biogenic materials with a crossed lamellar microstructure. Their occurrence is probably determined by the presence of shell organic components which regulate crystal growth and may favor unusual crystallographic relationships. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
issn 1742-7061
year published 2012
volume 8
issue 2
beginning page 830
ending page 835
digital object identifier (doi) 10.1016/j.actbio.2011.11.001
web of science category Engineering, Biomedical; Materials Science, Biomaterials
subject category Engineering; Materials Science
unique article identifier WOS:000301081400039
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