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Polymorphic Transition in Biogenic Calcium Carbonate: Nacre/Prismatic Interface in Abalone Shell

Published online by Cambridge University Press:  02 July 2020

Daniel M. Freeh
Affiliation:
Materials Science and Engineering, University of Washington, Seattle, WA98195, USA
Mehmet Sarikaya
Affiliation:
Materials Science and Engineering, University of Washington, Seattle, WA98195, USA
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Extract

The research in biological hard tissues offers lessons for biomimetic (structure and processing) strategies, such as for the synthesis of hierarchical architectures tailored for specific engineering applications. These biocomposites, i.e., biogenic materials in which the major phase is an inorganic component associated with macromolecules (proteins and polysaccharides), include bones, dentin, sea-urchin skeletal units, bacterial and algal particles and molluscan shells. Here, a summary is given from a recent TEM study of the interfacial region of nacreous and prismatic sections of red abalone shell to understand the morphological and crystallographic correlations across this transition region.

Many mollusk species have shells made of CaCO3 in various architectures that have evolved under different ecological conditions to produce structures that best protect the organism. The shells of many species contain both aragonite (orthorhombic, Pmnc) and calcite (Rhombohedral, R3m). In red abalone (Haliotis rufescens), the outer section, prismatic (P), is composed of columnar crystallites of calcite (1-5 μm base, 5-10 μm height), and the inner section, nacre (N), is composed of pseudo-hexagonal platelets of aragonite (side 2-5 μm), stacked as 0.25 μm layers, separated by a few nm-thick organic layer (Fig. 1).

Type
Ceramics and Ceramic Composites
Copyright
Copyright © Microscopy Society of America 1997

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References

1. Biomimetics, Sarikaya, M. and Aksay, I. A. (eds.) (AIP Press, New York 1995).Google Scholar

2. Morse, D.et al., U. C. Santa Barbara, private communications.Google Scholar