Nacre is a natural nano-laminar composite making up the inner shell structure of mollusks. It consists of ordered plates of the CaCO{sub}3 polymorph aragonite in an organic matrix, and known to have mechanical properties far greater than the monolithic ceramic. While making up less than 5% of the volume, the organic matrix in nacre is considered as playing a key role in the formation and mechanical behavior. While the micro-scale mechanical behavior of the nacreous plate layers is well known, deforming by mechanisms common to composite materials such as sliding, pullout, crack deflection, and interface separation, the mechanical behavior of the matrix is still largely unclear. In order to further understand its nano-scale structure and deformation, transmission electron microscopy (TEM) was used to directly observe the structure and deformation behavior of the organic matrix. Samples of nacre were partially demineralized to observe the structure of the organic material. The matrix between layers of aragonite plates (inter-layer matrix) was found to consist of perforated sheets with many holes, while the matrix between adjacent plates in a layer (inter-plate matrix) was relatively solid which suggested a material transport role of the inter-layer materix. Samples were also deformed in situ using a TEM straining holder to study the nano-scale deformation behavior of the organic matrix. Adhesion, bridging and high ductility of the organic material were observed, demonstrating its important role in toughening mechanisms.
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